Benzimidazole-carboxamide compounds as 5-ht4 receptor agonists

ABSTRACT

The invention relates to benzimidazole-carboxamide 5-HT 4  receptor agonist compounds of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein R 1  and X are as defined in the specification, or a pharmaceutically acceptable salt or solvate or stereoisomer thereof. The invention also relates to pharmaceutical compositions comprising such compounds, methods of using such compounds to treat diseases associated with 5-HT 4  receptor activity, and processes and intermediates useful for preparing such compounds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Applications Nos. 60/684,466 and 60/684,478, filed on May 25, 2005, and 60/748,415, filed on Dec. 8, 2005, the disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to benzimidazole-carboxamide compounds which are useful as 5-HT₄ receptor agonists. The invention is also directed to pharmaceutical compositions comprising such compounds, methods of using such compounds for treating or preventing medical conditions mediated by 5-HT₄ receptor activity, and processes and intermediates useful for preparing such compounds.

2. State of the Art

Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter that is widely distributed throughout the body, both in the central nervous system and in peripheral systems. At least seven subtypes of serotonin receptors have been identified and the interaction of serotonin with these different receptors is linked to a wide variety of physiological functions. There has been, therefore, substantial interest in developing therapeutic agents that target specific 5-HT receptor subtypes.

In particular, characterization of 5-HT₄ receptors and identification of pharmaceutical agents that interact with them has been the focus of significant recent activity. (See, for example, the review by Langlois and Fischmeister, J. Med. Chem. 2003, 46, 319-344.) 5-HT₄ receptor agonists are useful for the treatment of disorders of reduced motility of the gastrointestinal tract. Such disorders include irritable bowel syndrome (IBS), chronic constipation, functional dyspepsia, delayed gastric emptying, gastroesophageal reflux disease (GERD), gastroparesis, post-operative ileus, intestinal pseudo-obstruction, and drug-induced delayed transit. In addition, it has been suggested that some 5-HT₄ receptor agonist compounds may be used in the treatment of central nervous system disorders including cognitive disorders, behavioral disorders, mood disorders, and disorders of control of autonomic function.

Despite the broad utility of pharmaceutical agents modulating 5-HT₄ receptor activity, few 5-HT₄ receptor agonist compounds are in clinical use at present. Accordingly, there is a need for new 5-HT₄ receptor agonists that achieve their desired effects with minimal side effects. Preferred agents may possess, among other properties, improved selectivity, potency, pharmacokinetic properties, and/or duration of action.

SUMMARY OF THE INVENTION

The invention provides novel compounds that possess 5-HT₄ receptor agonist activity. Among other properties, compounds of the invention have been found to be potent and selective 5-HT₄ receptor agonists. In addition, preferred compounds of the invention have been found to exhibit favorable pharmacokinetic properties in an animal model which are predictive of good bioavailability upon oral administration.

Accordingly, the invention provides a compound of formula (I):

wherein:

R¹ is C₃₋₅alkyl, optionally substituted with —OH; and

X is selected from

-   -   (a) —C(O)OR² wherein R² is C₁₋₄alkyl or —(CH₂)_(n)-phenyl         wherein n is 0 or 1;     -   (b) —C(O)R³ wherein R³ is selected from:         -   phenyl, optionally substituted with 1, 2, or 3 substituents             selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃,             —OCHF₂, and —CN,         -   C₁₋₅alkyl,         -   C₄₋₅cycloalkyl, and         -   (CH₂)_(m)-A wherein m is 0 or 1 and A is selected from             amino, furanyl, thiophenyl, morpholinyl, tetrahydrofuranyl,             pyridinyl, naphthalenyl, pyrrolyl, thiomorpholinyl,             pyrrolidinyl, piperidinyl, oxoazetidinyl, thiazolidinyl,             1,1-dioxo isothiazolidinyl, and 2,4-dimethylisoxazolyl;     -   (c) —C(O)NR⁴R⁵ wherein R⁴ is hydrogen or C₁₋₃alkyl, and R⁵ is         phenyl optionally substituted with 1, 2, or 3 substituents         selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, and         —OCHF₂;     -   (d) —C(O)C(R⁶R⁷)R⁸ wherein R⁶ is hydrogen or C₁₋₃alkyl and R⁷ is         hydrogen, —OH, or C₁₋₃alkyl; or R⁶ and R⁷ taken together form         oxo or —(CH₂)₂—; and R⁸ is phenyl or cyclohexyl, wherein phenyl         or cyclohexyl are optionally substituted with 1, 2, or 3         substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃,         —OCF₃, —OCHF₂, and —CN;     -   (e) —C(O)C(HR⁹)OR¹⁰ wherein R⁹ is hydrogen or C₁₋₃alkyl, and R¹⁰         is phenyl optionally substituted with 1, 2, or 3 substituents         selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, and         —OCHF₂; and     -   (f) —S(O)₂R¹¹ wherein R¹¹ is selected from C₁₋₃alkyl,         —CH₂-phenyl, furanyl, thiophenyl, morpholinyl,         tetrahydrofuranyl, pyridinyl, naphthalenyl, pyrrolyl,         thiomorpholinyl, pyrrolidinyl, piperidinyl, oxoazetidinyl,         thiazolidinyl, 1,1-dioxo isothiazolidinyl,         2,4-dimethylisoxazolyl, and phenyl optionally substituted with         1, 2, or 3 substituents selected from C₁₋₄alkyl, halo,         C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN;

or a pharmaceutically-acceptable salt or solvate or stereoisomer thereof.

The invention also provides a pharmaceutical composition comprising a compound of the invention and a pharmaceutically-acceptable carrier.

In another aspect, the invention provides a method of treating a disease or condition associated with 5-HT₄ receptor activity, e.g. a disorder of reduced motility of the gastrointestinal tract, the method comprising administering to the mammal, a therapeutically effective amount of a compound of the invention.

Further, the invention provides a method of treating a disease or condition associated with 5-HT₄ receptor activity in a mammal, the method comprising administering to the mammal, a therapeutically effective amount of a pharmaceutical composition of the invention.

The compounds of the invention can also be used as research tools, i.e. to study biological systems or samples, or for studying the activity of other chemical compounds. Accordingly, in another of its method aspects, the invention provides a method of using a compound of formula (I), or a pharmaceutically acceptable salt or solvate or stereoisomer thereof, as a research tool for studying a biological system or sample or for discovering new 5-HT₄ receptor agonists, the method comprising contacting a biological system or sample with a compound of the invention and determining the effects caused by the compound on the biological system or sample.

In separate and distinct aspects, the invention also provides synthetic processes and intermediates described herein, which are useful for preparing compounds of the invention.

The invention also provides a compound of the invention as described herein for use in medical therapy, as well as the use of a compound of the invention in the manufacture of a formulation or medicament for treating a disease or condition associated with 5-HT₄ receptor activity, e.g. a disorder of reduced motility of the gastrointestinal tract, in a mammal.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides novel benzimidazole-carboxamide 5-HT₄ receptor agonists of formula (I), or pharmaceutically-acceptable salts or solvates or stereoisomers thereof. The following substituents and values are intended to provide representative examples of various aspects of this invention. These representative values are intended to further define such aspects and are not intended to exclude other values or limit the scope of the invention.

In a specific aspect of the invention, R¹ is C₃₋₅alkyl, optionally substituted with —OH.

In another specific aspect, R¹ is C₃₋₅alkyl.

In other specific aspects, R¹ is C₃₋₄alkyl; or R¹ is isopropyl or tert-butyl.

In another specific aspect, R¹ is isopropyl.

In yet other specific aspects, R¹ is 1-hydroxy-1-methylethyl, or 2-hydroxy-1-methylethyl.

In a specific aspect, X is —C(O)OR² wherein R² is C₁₋₄alkyl or —(CH₂)_(n)-phenyl wherein n is 0 or 1.

In another specific aspect, X is —C(O)OR² wherein R² is C₁₋₃alkyl or phenyl.

In other specific aspects, X is —C(O)OR² wherein R² is methyl or phenyl, or wherein R² is methyl.

In a specific aspect, X is —C(O)R³ wherein R³ is selected from phenyl, optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄ alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN; C₁₋₅alkyl; C₄₋₅cycloalkyl; and —(CH₂)_(m)-A wherein m is 0 or 1 and A is selected from amino, furanyl, thiophenyl, morpholinyl, tetrahydrofuranyl, pyridinyl, naphthalenyl, pyrrolyl, thiomorpholinyl, pyrrolidinyl, piperidinyl, oxoazetidinyl, thiazolidinyl, 1,1-dioxo isothiazolidinyl, and 2,4-dimethylisoxazolyl.

In another specific aspect, X is —C(O)R³ wherein R³ is phenyl, optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN.

In another specific aspect, X is —C(O)R³ wherein R³ is C₁₋₅alkyl or C₄₋₅cycloalkyl.

In another specific aspect, X is —C(O)R³ wherein R³ is —(CH₂)_(m)-A wherein m is 0 and A is selected from amino, furanyl, thiophenyl, morpholinyl, tetrahydrofuranyl, pyridinyl, naphthalenyl, pyrrolyl, thiomorpholinyl, pyrrolidinyl, piperidinyl, oxoazetidinyl, thiazolidinyl, 1,1-dioxo isothiazolidinyl, and 2,4-dimethylisoxazolyl.

In another specific aspect, X is —C(O)R³ wherein R³ is phenyl, optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl, halo, and —CF₃; furanyl; or thiophenyl.

In yet other specific aspects, X is —C(O)R³ wherein R³ is phenyl optionally substituted with 1 or 2 substituents selected from methyl, chloro, fluoro, and —CF₃; or R³ is furan-2-yl or thiophen-2-yl.

In a specific aspect, X is —C(O)NR⁴R⁵ wherein R⁴ is hydrogen or C₁₋₃alkyl, and R⁵ is phenyl optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, and —OCHF₂.

In another specific aspect, X is —C(O)NR⁴R⁵ wherein R⁴ is hydrogen.

In another specific aspect, X is —C(O)NR⁴R⁵ wherein R⁴ is hydrogen and R⁵ is phenyl optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo.

In other specific aspects, X is —C(O)NR⁴R⁵ wherein R⁴ is hydrogen and R⁵ is phenyl optionally substituted with 1 halo, or with one fluoro or chloro.

In a specific aspect, X is —C(O)C(R⁶R⁷)R⁸ wherein R⁶ is hydrogen or C₁₋₃alkyl and R⁷ is hydrogen, —OH, or C₁₋₃alkyl; or R⁶ and R⁷ taken together form oxo or —(CH₂)₂—; and R⁸ is phenyl or cyclohexyl, wherein phenyl or cyclohexyl are optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN.

In another specific aspect, X is —C(O)C(R⁶R⁷)R⁸ wherein R⁶ is hydrogen.

In another specific aspect, X is —C(O)C(R⁶R⁷)R⁸ wherein R⁸ is phenyl optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN.

In another specific aspect, X is —C(O)C(R⁶R⁷)R⁸ wherein R⁸ is cyclohexyl optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN.

In yet other specific aspects, X is —C(O)C(R⁶R⁷)R⁸ wherein R⁶ is hydrogen and R⁷ is hydrogen, —OH, or methyl; or R⁶ and R⁷ taken together form oxo or —(CH₂)₂—; and R⁸ is phenyl or cyclohexyl, wherein phenyl or cyclohexyl are optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo; or R⁸ is phenyl or cyclohexyl, wherein phenyl or cyclohexyl are optionally substituted with 1 or 2 substituents selected from methyl, fluoro, and chloro.

In a specific aspect, X is —C(O)C(HR⁹)OR¹⁰ wherein R⁹ is hydrogen or C₁₋₃alkyl, and R¹⁰ is phenyl optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, and —OCHF₂.

In another specific aspect, X is —C(O)C(HR⁹)OR¹⁰ wherein R⁹ is hydrogen or methyl.

In other specific aspects, X is —C(O)C(HR⁹)OR¹⁰ wherein R⁹ is hydrogen or methyl and R¹⁰ is phenyl optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo, or phenyl optionally substituted with 1 or 2 substituents selected from methyl, fluoro, and chloro.

In a specific aspect, X is —S(O)₂R¹¹ wherein R¹¹ is selected from C₁₋₃alkyl, —CH₂-phenyl, furanyl, thiophenyl, morpholinyl, tetrahydrofuranyl, pyridinyl, naphthalenyl, pyrrolyl, thiomorpholinyl, pyrrolidinyl, piperidinyl, oxoazetidinyl, thiazolidinyl, 1,1-dioxo isothiazolidinyl, 2,4-dimethylisoxazolyl, and phenyl optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN.

In another specific aspect, X is —S(O)₂R¹¹ wherein R¹¹ is C₁₋₃alkyl, 2,4-dimethylisoxazolyl, or phenyl, optionally substituted with 1, 2, or 3 substituents selected from C₁₋₄alkyl, halo, C₁₋₄alkoxy, —CF₃, —OCF₃, —OCHF₂, and —CN.

In other specific aspects, X is —S(O)₂R¹¹ wherein R¹¹ is methyl or phenyl optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo; or with 1 or 2 substituents selected from methyl, fluoro, and chloro.

In one aspect, the invention provides a compound of formula (I) wherein

R¹ is C₃₋₄alkyl; and

X is selected from:

-   -   (a) —C(O)OR² wherein R² is C₁₋₃alkyl or phenyl;     -   (b) —C(O)R³ wherein R³ is phenyl, optionally substituted with 1         or 2 substituents selected from C₁₋₄alkyl, halo, and —CF₃;         furanyl; or thiophenyl;     -   (c) —C(O)NR⁴R⁵ wherein R⁴ is hydrogen and R⁵ is phenyl         optionally substituted with 1 or 2 substituents selected from         C₁₋₄alkyl and halo;     -   (d) —C(O)C(R⁶R⁷)R⁸ wherein R⁶ is hydrogen and R⁷ is hydrogen,         —OH, or methyl; or R⁶ and R⁷ taken together form oxo or         —(CH₂)₂—; and R⁸ is phenyl or cyclohexyl, wherein phenyl or         cyclohexyl are optionally substituted with 1 or 2 substituents         selected from C₁₋₄alkyl and halo;     -   (e) —C(O)C(HR⁹)OR¹⁰ wherein R⁹ is hydrogen or methyl and R¹⁰ is         phenyl optionally substituted with 1 or 2 substituents selected         from C₁₋₄alkyl and halo; and

(f) —S(O)₂R¹¹ wherein R¹¹ is methyl or phenyl, optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo.

The invention further provides a compound of formula (I) wherein:

R¹ is isopropyl or tert-butyl; and

X is selected from:

-   -   (a) —C(O)OR² wherein R² is methyl or phenyl;     -   (b) —C(O)R³ wherein R³ is phenyl, optionally substituted with 1         or 2 substituents selected from methyl, chloro, fluoro, and         —CF₃; furan-2-yl; or thiophen-2-yl; and     -   (c) —C(O)NR⁴R⁵ wherein R⁴ is hydrogen and R⁵ is phenyl         optionally substituted with 1 fluoro or chloro.

In still other specific aspects, the invention provides the compounds listed in the Examples and in Tables I to IX below.

The chemical naming convention used herein is illustrated for the compound of Example 1:

which is designated 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester, according to the AutoNom software, provided by MDL Information Systems, GmbH (Frankfurt, Germany). The fused ring structure “benzoimidazole” is alternatively named “benzimidazole”. The two terms are equivalent as used herein.

As exemplified by particular compounds listed in the tables below, the compounds of the invention may contain a chiral center. Accordingly, the invention includes racemic mixtures, pure stereoisomers, and stereoisomer-enriched mixtures of such isomers, unless otherwise indicated. When a particular stereoisomer is shown, it will be understood by those skilled in the art, that minor amounts of other stereoisomers may be present in the compositions of the invention unless otherwise indicated, provided that any utility of the composition as a whole is not eliminated by the presence of such other isomers.

In one aspect, the invention provides a compound selected from:

-   4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic     acid methyl ester; -   4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]-methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic     acid phenyl ester; -   2-isopropyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(2-chlorobenzoyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; -   2-isopropyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(2,4-difluoro-benzoyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; -   2-isopropyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(furan-2-carbonyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; -   2-isopropyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(thiophene-2-carbonyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; -   2-isopropyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(2-fluoro-5-trifluoromethylbenzoylpiperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; -   2-isopropyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(2-fluoro-phenylcarbamoyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}-amide; -   4-(4-{[(2-tert-butyl-1H-benzoimidazole-4-carbonyl)-amino]-methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic     acid methyl ester; -   2-tert-butyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(2-fluoro-benzoyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; -   2-tert-butyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(3-methyl-benzoyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide;     and -   2-tert-butyl-1H-benzoimidazole-4-carboxylic acid     {1-[1-(4-fluorobenzoyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide.

DEFINITIONS

When describing the compounds, compositions and methods of the invention, the following terms have the following meanings, unless otherwise indicated.

The term “alkyl” means a monovalent saturated hydrocarbon group which may be linear or branched or combinations thereof. Unless otherwise defined, such alkyl groups typically contain from 1 to 10 carbon atoms. Representative alkyl groups include, by way of example, methyl (Me), ethyl, n-propyl (n-Pr), isopropyl (iPr), n-butyl (n-Bu), sec-butyl, isobutyl, tert-butyl (tBu), n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl and the like.

The term “alkoxy” means a monovalent group —O-alkyl, where alkyl is defined as above. Representative alkoxy groups include, by way of example, methoxy, ethoxy, propoxy, butoxy, and the like.

The term “cycloalkyl” means a monovalent saturated carbocyclic group which may be monocyclic or multicyclic. Unless otherwise defined, such cycloalkyl groups typically contain from 3 to 10 carbon atoms. Representative cycloalkyl groups include, by way of example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and the like.

The term “halo” means fluoro, chloro, bromo or iodo.

The term “oxo” means a double-bonded oxygen atom (═O).

The term “compound” means a compound that was synthetically prepared or produced in any other way, such as by metabolism.

The term “therapeutically effective amount” means an amount sufficient to effect treatment when administered to a patient in need of treatment.

The term “treatment” as used herein means the treatment of a disease, disorder, or medical condition in a patient, such as a mammal (particularly a human) which includes:

-   -   (a) preventing the disease, disorder, or medical condition from         occurring, i.e., prophylactic treatment of a patient;     -   (b) ameliorating the disease, disorder, or medical condition,         i.e., eliminating or causing regression of the disease,         disorder, or medical condition in a patient;     -   (c) suppressing the disease, disorder, or medical condition,         i.e., slowing or arresting the development of the disease,         disorder, or medical condition in a patient; or     -   (d) alleviating the symptoms of the disease, disorder, or         medical condition in a patient.

The term “pharmaceutically-acceptable salt” means a salt prepared from an acid or base which is acceptable for administration to a patient, such as a mammal. Such salts can be derived from pharmaceutically-acceptable inorganic or organic acids and from pharmaceutically-acceptable bases. Typically, pharmaceutically-acceptable salts of compounds of the present invention are prepared from acids.

Salts derived from pharmaceutically-acceptable acids include, but are not limited to, acetic, adipic, benzenesulfonic, benzoic, camphorsulfonic, citric, ethanesulfonic, fumaric, gluconic, glutamic, hydrobromic, hydrochloric, lactic, maleic, malic, mandelic, methanesulfonic, mucic, nitric, pantothenic, phosphoric, succinic, sulfuric, tartaric, p-toluenesulfonic, xinafoic (1-hydroxy-2-naphthoic acid), naphthalene-1,5-disulfonic acid and the like.

The term “solvate” means a complex or aggregate formed by one or more molecules of a solute, i.e. a compound of the invention or a pharmaceutically-acceptable salt thereof, and one or more molecules of a solvent. Such solvates are typically crystalline solids having a substantially fixed molar ratio of solute and solvent. Representative solvents include by way of example, water, methanol, ethanol, isopropanol, acetic acid, and the like. When the solvent is water, the solvate formed is a hydrate.

It will be appreciated that the term “or a pharmaceutically-acceptable salt or solvate of stereoisomer thereof” is intended to include all permutations of salts, solvates and stereoisomers, such as a solvate of a pharmaceutically-acceptable salt of a stereoisomer of a compound of formula (I).

The term “amino-protecting group” means a protecting group suitable for preventing undesired reactions at an amino nitrogen. Representative amino-protecting groups include, but are not limited to, formyl; acyl groups, for example alkanoyl groups, such as acetyl; alkoxycarbonyl groups, such as tert-butoxycarbonyl (Boc); arylmethoxycarbonyl groups, such as benzyloxycarbonyl (Cbz) and 9-fluorenylmethoxycarbonyl (Fmoc); arylmethyl groups, such as benzyl (Bn), trityl (Tr), and 1,1-di-(4′-methoxyphenyl)methyl; silyl groups, such as trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBDMS); and the like.

General Synthetic Procedures

Compounds of the invention can be prepared from readily available starting materials using the following general methods and procedures. Although a particular aspect of the present invention is illustrated in the schemes below, those skilled in the art will recognize that all aspects of the present invention can be prepared using the methods described herein or by using other methods, reagents and starting materials known to those skilled in the art. It will also be appreciated that where typical or preferred process conditions (i.e., reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions can also be used unless otherwise stated. Optimum reaction conditions may vary with the particular reactants or solvent used, but such conditions can be determined by one skilled in the art by routine optimization procedures.

Additionally, as will be apparent to those skilled in the art, conventional protecting groups may be necessary to prevent certain functional groups from undergoing undesired reactions. The choice of a suitable protecting group for a particular functional group, as well as suitable conditions for protection and deprotection, are well known in the art. For example, numerous protecting groups, and their introduction and removal, are described in T. W. Greene and G. M. Wuts, Protecting Groups in Organic Synthesis, Third Edition, Wiley, New York, 1999, and references cited therein.

In one method of synthesis, compounds of formula (I) are prepared by reacting a piperidinylmethyl-piperidinylmethyl intermediate of formula (II):

with a reagent of formula (III):

L—X  (III)

where L is a leaving group, for example a halo, such as chloro, or an acyloxy, sulfonic ester, or oxysuccinimide, and R¹ and X are defined as in formula (I).

The reaction is typically conducted by contacting intermediate (II) with between about 1 and about 1.5 equivalents of intermediate (III) in a polar aprotic diluent, such as dichloromethane, in the presence of at least one equivalent of an amine base, such as N,N-diisopropylethylamine. Suitable inert diluents for this process and those described below, also include N,N-dimethylformamide, trichloromethane, 1,1,2,2-tetrachloroethane, tetrahydrofuran, and the like. Suitable amine bases for the processes of the present invention also include triethylamine, pyridine, and the like. The reaction is typically conducted at a temperature in the range of about 0° C. to about 30° C. for about a quarter hour to about 2 hours, or until the reaction is substantially complete. Exemplary reagents L—X in which L is chloro include methyl chloroformate, phenyl chloroformate, chlorobenzoyl chloride, and methanesulfonyl chloride.

In an alternative method of synthesis, compounds of formula (I) in which X is selected from —C(O)R³, —C(O)C(R⁶R⁷)R⁸, and —C(O)C(HR⁹)OR¹⁰ can be prepared by the amide coupling reaction of an intermediate of formula (II) with a carboxylic acid of formula (IV):

In formula (IV), X′ represents R³, C(R⁶R⁷)R⁸, or C(HR⁹)OR¹⁰, such that —C(O)X′ corresponds to X, as set forth above formula (IV). In the amide coupling reaction of intermediate (II), between about 1 and about 1.5 equivalents of the carboxylic acid (IV) are first contacted with between 1 and about 1.5 equivalents of a coupling agent such as O-(7-axabenzotrizol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU) in a polar aprotic solvent such as dimethylformamide or those discussed above. The acid mixture is then contacted with intermediate (II) in the presence of between about 2 and about 4 equivalents of an amine base, for example, N,N-diisopropylethylamine. The reaction is typically conducted at a temperature in the range of about 0° C. to about 30° C. for about a quarter hour to about 2 hours, or until the reaction is substantially complete.

Suitable alternative coupling agents include N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), 1,1′-carbonyldiimidazole (CDI) 1,3 dicyclohexylcarbodiimide (DCC), and benzotriazol-1-yloxytripyrrolidino-phosphonium hexafluorophosphate (PyBop). The coupling agents may be combined with promoting agents, for example, 1-hydroxy-7-azabenzotriazole (HOAt), hydroxybenzotriazole (HOBt), or 1,4-diazabicyclo[2,2,2]octane (DABCO).

In yet another alternative process, compounds of formula (I) in which X is —C(O)NHR⁵ can be prepared by reacting an intermediate of formula (II) with an isocyanate of the form:

O═C═N—R⁵  (V)

The reaction is typically conducted by contacting intermediate (II) with between about 1 and about 1.5 equivalents of intermediate (V) in a polar aprotic diluent in the presence of at between about 2 and about 4 equivalents of an amine base. The reaction is typically conducted at a temperature in the range of about 0° C. to about 30° C. for about a quarter hour to about 24 hours, or until the reaction is substantially complete.

The product of formula (I) is isolated and purified by conventional procedures. For example, the product can be concentrated to dryness under reduced pressure and the residue purified by HPLC chromatography.

The piperidinylmethyl-piperidinylmethyl intermediates of formula (II) are prepared from readily available starting materials by the procedure illustrated in Scheme A.

where P¹ and P² independently represent an amino protecting group, such as tert-butoxycarbonyl (Boc).

First, a carboxylic acid of formula (VI) is reacted with a protected aminomethyl piperidine to form a protected intermediate of formula (VII). This reaction is typically conducted by contacting (VI) with between about 1 and about 2 equivalents of protected aminomethylpiperidine in a polar aprotic diluent, in the presence of an amide coupling agent described above, for example N-ethyl-N-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) combined with hydroxybenzotriazole (HOBt) or 1,1′-carbonyldiimidazole (CDI) combined with 1,4-diazabicyclo[2,2,2]octane (DABCO). The reaction is typically conducted at a temperature in the range of about 0° C. to about 60° C. for between about 1 and about 24 hours or until the reaction is substantially complete.

The protecting group P¹ is removed from intermediate (VII) by conventional means to provide intermediate (VIII). For example, when Boc is used as the protecting group, it may be removed by treatment with an acid, such as trifluoroacetic acid or hydrochloric acid.

An intermediate of formula (IX) is then formed by the reductive amination of intermediate (VIII) with a protected piperidine-carboxaldehyde. This reaction is typically conducted by contacting (VIII) with between about 1 and about 2 equivalents of the protected piperidine-carboxaldehyde in an inert diluent in the presence of between about 1 and about 2 equivalents of a reducing agent. Optionally, about one equivalent of a weak acid, such as acetic acid can be included to accelerate the reaction. The reaction may be conducted at a temperature between about 0° C. and about 30° C., typically between about 20° C. and about 30° C., for about 0.25 to about 2 hours, or until the reaction is substantially complete.

Suitable inert diluents include dichloromethane, trichloromethane, 1,1,2,2-tetrachloroethane, and the like. Typical reducing agents include sodium triacetoxyborohydride, sodium borohydride, and sodium cyanoborohydride. The product (IX) is isolated by standard procedures. When the amine (VIII) is supplied as an acid salt, typically between about 1 and about 3 equivalents of an amine base, such as N,N-diisopropylethylamine, is included in the reaction. Finally, the protecting group P² is removed from intermediate (IX) by conventional procedures to provide the piperidinylmethyl-piperidinylmethyl intermediate (II).

A carboxylic acid of formula (VI) can be prepared from a diaminobenzoic acid or ester by the process illustrated in Scheme B:

where R represents methyl or hydrogen. Intermediate (XI) is reacted with a carboxylic acid R¹C(O)OH to form the acid intermediate (VI). This reaction is typically conducted by contacting the acid or ester (XI) with between about 2 and about 4 equivalents of the carboxylic acid R¹C(O)OH in an aqueous acidic solution. The reaction is typically conducted at a temperature in the range of about 80° C. to about 100° C. for about 12 to about 72 hours. The pH of the solution is then raised by the addition of base, such as sodium hydroxide, and the product isolated by conventional means.

A convenient process for providing intermediate (XI) as the methyl ester uses 2-amino-3-nitrobenzoic acid methyl ester (X):

as the starting material. Typically, 2-amino-3-nitrobenzoic acid methyl ester (X) is dissolved in a polar diluent and reduced by exposure to a hydrogen atmosphere in the presence of a transition metal catalyst to provide the diaminobenzoic acid methyl ester (XI). The reaction is typically conducted at ambient temperature for about 12 to about 72 hours.

When the substituent R¹ is sterically bulky, as for example, when R¹ is tert-butyl, tert-butylbenzimidazole carboxylic acid (VI′) can be prepared by the conversion of methyl ester (XI′) according to a two-step process, as illustrated, for example, in Scheme C:

As described in detail in Preparation 3 below, the methyl ester (XI′) is first reacted with 2,2-dimethylpropionyl chloride to provide the intermediate (XII) which is refluxed in a strong acid solution, typically, for between about 12 and about 72 hours, to provide the tert-butylbenzimidazole carboxylic acid (VI′).

In alternative methods of synthesis, compounds of formula (I) can be prepared according to the process routes illustrated in Scheme D using the reductive amination and other reactions described above, and/or using alternative reactions well known to those skilled in the art.

As shown in process route (i), an intermediate of formula (VIII) is reacted with an intermediate of formula (XIII) to provide a compound of formula (I). The reaction is typically performed under the conditions described above for the reaction of amine (VIII) with the protected piperidine-carboxaldehyde in Scheme A.

Intermediate (XIII) can be prepared by the reaction of 4-hydroxymethylpiperidine with a reagent L—X, of formula (III), followed by oxidation of the resulting intermediate. For example, for the particular case of X is —C(O)OCH₃, intermediate (XIII) can be prepared as shown in Scheme E.

First 4-hydroxymethylpiperidine is reacted with methylchloroformate to form the hydroxymethylpiperidine intermediate (XV). The reaction is typically conducted by contacting 4-hydroxymethylpiperidine in an aqueous solution with between about 3 and about 5 equivalents of methylchloroformate in the presence of between about 3 and about 5 equivalents of base. The reaction is typically conducted at a temperature in the range of about 0° C. to about 30° C. for about 12 to about 72 hours or until the reaction is substantially complete. Intermediate (XV) is then oxidized to form the formylpiperidinyl intermediate (XIII′) The oxidation reaction typically makes use of an oxidation reagent such as a combination of oxalyl chloride and dimethylsulfoxide (Sween oxidation), a chromate reagent, such as pyridinium chlorochromate, or an oxidizing agent, such as sodium hypochlorite, together with a catalyst such as 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO).

The preparation of a compound of formula (I) according to process route (i) of Scheme D using intermediate (XIII′) is described in Examples 214 and 216 below.

A compound of formula (I) can also be prepared by reacting a carboxylic acid of formula (VI) with an intermediate of formula (XIV), as shown in process route (ii). As illustrated in Scheme F, intermediate (XIV) can be prepared by the reaction of a protected aminomethylpiperidine with intermediate (XIII):

where P is an amino-protecting group, to provide a protected intermediate of formula (XVI), followed by a deprotection step. The preparation of compounds according to process route (ii) is described in Preparation 4 and in Examples 14 and 15 below.

The reagents L—X (III), X′C(O)OH (IV), O═C═N═R⁵ (V) and R¹C(O)OH are available commercially or are readily prepared by standard procedures from common starting materials.

Further details regarding specific reaction conditions and other procedures for preparing representative compounds of the invention or intermediates thereto are described in the examples below.

Accordingly, in a method aspect, the invention provides a process for preparing a compound of formula (I), or a salt or stereoisomer thereof, the process comprising (a) reacting a compound of formula (II) with compound of the formula (II); (b) reacting a compound formula (VIII) with a compound of formula (XIII); or (c) reacting a compound of formula (VI) with a compound of formula (XIV) to provide a compound of formula (I), or a salt or stereoisomer thereof.

In an additional method aspect, the invention provides a process for preparing a compound of formula (I) wherein X is selected from —C(O)R³, —C(O)C(R⁶R⁷)R⁸, and —C(O)C(HR⁹)OR¹⁰, or a salt or stereoisomer thereof, the process comprising reacting a compound of formula (II) with a compound of formula (IV), wherein X′ represents R³, C(R⁶R⁷)R⁸, or C(HR⁹)OR¹⁰, to provide a compound of formula (I), or a salt or stereoisomer thereof.

The invention further provides a compound of formula (II), or a salt or stereoisomer or protected derivative thereof, wherein R¹ is defined as in formula (I).

Pharmaceutical Compositions

The benzimidazole-carboxamide compounds of the invention are typically administered to a patient in the form of a pharmaceutical composition. Such pharmaceutical compositions may be administered to the patient by any acceptable route of administration including, but not limited to, oral, rectal, vaginal, nasal, inhaled, topical (including transdermal) and parenteral modes of administration.

Accordingly, in one of its compositions aspects, the invention is directed to a pharmaceutical composition comprising a pharmaceutically-acceptable carrier or excipient and a therapeutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt or solvate thereof. Optionally, such pharmaceutical compositions may contain other therapeutic and/or formulating agents if desired.

The pharmaceutical compositions of the invention typically contain a therapeutically effective amount of a compound of the present invention or a pharmaceutically-acceptable salt thereof. Typically, such pharmaceutical compositions will contain from about 0.1 to about 95% by weight of the active agent; including from about 5 to about 70% by weight; and from about 10 to about 60% by weight of the active agent.

Any conventional carrier or excipient may be used in the pharmaceutical compositions of the invention. The choice of a particular carrier or excipient, or combinations of carriers or excipients, will depend on the mode of administration being used to treat a particular patient or type of medical condition or disease state. In this regard, the preparation of a suitable pharmaceutical composition for a particular mode of administration is well within the scope of those skilled in the pharmaceutical arts. Additionally, the ingredients for such compositions are commercially-available from, for example, Sigma, P.O. Box 14508, St. Louis, Mo. 63178. By way of further illustration, conventional formulation techniques are described in Remington: The Science and Practice of Pharmacy, 20^(th) Edition, Lippincott Williams & White, Baltimore, Md. (2000); and H. C. Ansel et al., Pharmaceutical Dosage Forms and Drug Delivery Systems, 7^(th) Edition, Lippincott Williams & White, Baltimore, Md. (1999).

Representative examples of materials which can serve as pharmaceutically acceptable carriers include, but are not limited to, the following: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, such as microcrystalline cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer's solution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxic compatible substances employed in pharmaceutical compositions.

The pharmaceutical compositions of the invention are typically prepared by thoroughly and intimately mixing or blending a compound of the invention with a pharmaceutically-acceptable carrier and one or more optional ingredients. If necessary or desired, the resulting uniformly blended mixture can then be shaped or loaded into tablets, capsules, pills and the like using conventional procedures and equipment.

The pharmaceutical compositions of the invention are preferably packaged in a unit dosage form. The term “unit dosage form” refers to a physically discrete unit suitable for dosing a patient, i.e., each unit containing a predetermined quantity of active agent calculated to produce the desired therapeutic effect either alone or in combination with one or more additional units. For example, such unit dosage forms may be capsules, tablets, pills, and the like.

In a preferred embodiment, the pharmaceutical compositions of the invention are suitable for oral administration. Suitable pharmaceutical compositions for oral administration may be in the form of capsules, tablets, pills, lozenges, cachets, dragees, powders, granules; or as a solution or a suspension in an aqueous or non-aqueous liquid; or as an oil-in-water or water-in-oil liquid emulsion; or as an elixir or syrup; and the like; each containing a predetermined amount of a compound of the present invention as an active ingredient.

When intended for oral administration in a solid dosage form (i.e., as capsules, tablets, pills and the like), the pharmaceutical compositions of the invention will typically comprise a compound of the present invention as the active ingredient and one or more pharmaceutically-acceptable carriers, such as sodium citrate or dicalcium phosphate. Optionally or alternatively, such solid dosage forms may also comprise: (1) fillers or extenders, such as starches, microcrystalline cellulose, lactose, sucrose, glucose, mannitol, and/or silicic acid; (2) binders, such as carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone, sucrose and/or acacia; (3) humectants, such as glycerol; (4) disintegrating agents, such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and/or sodium carbonate; (5) solution retarding agents, such as paraffin; (6) absorption accelerators, such as quaternary ammonium compounds; (7) wetting agents, such as cetyl alcohol and/or glycerol monostearate; (8) absorbents, such as kaolin and/or bentonite clay; (9) lubricants, such as talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, and/or mixtures thereof; (10) coloring agents; and (11) buffering agents.

Release agents, wetting agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the pharmaceutical compositions of the invention. Examples of pharmaceutically-acceptable antioxidants include: (1) water-soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfate sodium sulfite and the like; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate, alpha-tocopherol, and the like; and (3) metal-chelating agents, such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol, tartaric acid, phosphoric acid, and the like. Coating agents for tablets, capsules, pills and like, include those used for enteric coatings, such as cellulose acetate phthalate (CAP), polyvinyl acetate phthalate (PVAP), hydroxypropyl methylcellulose phthalate, methacrylic acid-methacrylic acid ester copolymers, cellulose acetate trimellitate (CAT), carboxymethyl ethyl cellulose (CMEC), hydroxypropyl methyl cellulose acetate succinate (HPMCAS), and the like.

If desired, the pharmaceutical compositions of the present invention may also be formulated to provide slow or controlled release of the active ingredient using, by way of example, hydroxypropyl methyl cellulose in varying proportions; or other polymer matrices, liposomes and/or microspheres.

In addition, the pharmaceutical compositions of the present invention may optionally contain opacifying agents and may be formulated so that they release the active ingredient only, or preferentially, in a certain portion of the gastrointestinal tract, optionally, in a delayed manner. Examples of embedding compositions which can be used include polymeric substances and waxes. The active ingredient can also be in micro-encapsulated form, if appropriate, with one or more of the above-described excipients.

Suitable liquid dosage forms for oral administration include, by way of illustration, pharmaceutically-acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. Such liquid dosage forms typically comprise the active ingredient and an inert diluent, such as, for example, water or other solvents, solubilizing agents and emulsifiers, such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (esp., cottonseed, groundnut, corn, germ, olive, castor and sesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan, and mixtures thereof. Suspensions, in addition to the active ingredient, may contain suspending agents such as, for example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth, and mixtures thereof.

Alternatively, the pharmaceutical compositions of the invention are formulated for administration by inhalation. Suitable pharmaceutical compositions for administration by inhalation will typically be in the form of an aerosol or a powder. Such compositions are generally administered using well-known delivery devices, such as a metered-dose inhaler, a dry powder inhaler, a nebulizer or a similar delivery device.

When administered by inhalation using a pressurized container, the pharmaceutical compositions of the invention will typically comprise the active ingredient and a suitable propellant, such as dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas.

Additionally, the pharmaceutical composition may be in the form of a capsule or cartridge (made, for example, from gelatin) comprising a compound of the invention and a powder suitable for use in a powder inhaler. Suitable powder bases include, by way of example, lactose or starch.

The compounds of the invention can also be administered transdermally using known transdermal delivery systems and excipients. For example, a compound of the invention can be admixed with permeation enhancers, such as propylene glycol, polyethylene glycol monolaurate, azacycloalkan-2-ones and the like, and incorporated into a patch or similar delivery system. Additional excipients including gelling agents, emulsifiers and buffers, may be used in such transdermal compositions if desired.

The following formulations illustrate representative pharmaceutical compositions of the present invention:

Formulation Example A

Hard gelatin capsules for oral administration are prepared as follows:

Ingredients Amount Compound of the invention 50 mg Lactose (spray-dried) 200 mg Magnesium stearate 10 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and then loaded into a hard gelatin capsule (260 mg of         composition per capsule).

Formulation Example B

Hard gelatin capsules for oral administration are prepared as follows:

Ingredients Amount Compound of the invention 20 mg Starch 89 mg Microcrystalline cellulose 89 mg Magnesium stearate 2 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and then passed through a No. 45 mesh U.S. sieve and loaded into         a hard gelatin capsule (200 mg of composition per capsule).

Formulation Example C

Capsules for oral administration are prepared as follows:

Ingredients Amount Compound of the invention 10 mg Polyoxyethylene sorbitan monooleate 50 mg Starch powder 250 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and then loaded into a gelatin capsule (310 mg of composition         per capsule).

Formulation Example D

Tablets for oral administration are prepared as follows:

Ingredients Amount Compound of the invention 5 mg Starch 50 mg Microcrystalline cellulose 35 mg Polyvinylpyrrolidone (10 wt. % in water) 4 mg Sodium carboxymethyl starch 4.5 mg Magnesium stearate 0.5 mg Talc 1 mg

-   -   Representative Procedure: The active ingredient, starch and         cellulose are passed through a No. 45 mesh U.S. sieve and mixed         thoroughly. The solution of polyvinylpyrrolidone is mixed with         the resulting powders, and this mixture is then passed through a         No. 14 mesh U.S. sieve. The granules so produced are dried at         50-60° C. and passed through a No. 18 mesh U.S. sieve. The         sodium carboxymethyl starch, magnesium stearate and talc         (previously passed through a No. 60 mesh U.S. sieve) are then         added to the granules. After mixing, the mixture is compressed         on a tablet machine to afford a tablet weighing 100 mg.

Formulation Example E

Tablets for oral administration are prepared as follows:

Ingredients Amount Compound of the invention 25 mg Microcrystalline cellulose 400 mg Silicon dioxide fumed 10 mg Stearic acid 5 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and then compressed to form tablets (440 mg of composition per         tablet).

Formulation Example F

Single-scored tablets for oral administration are prepared as follows:

Ingredients Amount Compound of the invention 15 mg Cornstarch 50 mg Croscarmellose sodium 25 mg Lactose 120 mg Magnesium stearate 5 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and compressed to form a single-scored tablet (215 mg of         compositions per tablet).

Formulation Example G

A suspension for oral administration is prepared as follows:

Ingredients Amount Compound of the invention 0.1 g Fumaric acid 0.5 g Sodium chloride 2.0 g Methyl paraben 0.15 g Propyl paraben 0.05 g Granulated sugar 25.5 g Sorbitol (70% solution) 12.85 g Veegum k (Vanderbilt Co.) 1.0 g Flavoring 0.035 mL Colorings 0.5 mg Distilled water q.s. to 100 mL

-   -   Representative Procedure: The ingredients are mixed to form a         suspension containing 10 mg of active ingredient per 10 mL of         suspension.

Formulation Example H

A dry powder for administration by inhalation is prepared as follows:

Ingredients Amount Compound of the invention 1.0 mg Lactose 25 mg

-   -   Representative Procedure: The active ingredient is micronized         and then blended with lactose. This blended mixture is then         loaded into a gelatin inhalation cartridge. The contents of the         cartridge are administered using a powder inhaler.

Formulation Example I

A dry powder for administration by inhalation in a metered dose inhaler is prepared as follows:

-   -   Representative Procedure: A suspension containing 5 wt. % of a         compound of the invention and 0.1 wt. % lecithin is prepared by         dispersing 10 g of active compound as micronized particles with         mean size less than 10 μm in a solution formed from 0.2 g of         lecithin dissolved in 200 mL of demineralized water. The         suspension is spray dried and the resulting material is         micronized to particles having a mean diameter less than 1.5 μm.         The particles are loaded into cartridges with pressurized         1,1,1,2-tetrafluoroethane.

Formulation Example J

An injectable formulation is prepared as follows:

Ingredients Amount Compound of the invention 0.2 g Sodium acetate buffer solution (0.4M) 40 mL HCl (0.5N) or NaOH (0.5N) q.s. to pH 4 Water (distilled, sterile) q.s. to 20 mL

-   -   Representative Procedure: The above ingredients are blended and         the pH is adjusted to 4±0.5 using 0.5 N HCl or 0.5 N NaOH.

Formulation Example K

Capsules for oral administration are prepared as follows:

Ingredients Amount Compound of the Invention 4.05 mg Microcrystalline cellulose (Avicel PH 103) 259.2 mg Magnesium stearate 0.75 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and then loaded into a gelatin capsule (Size #1, White, Opaque)         (264 mg of composition per capsule).

Formulation Example L

Capsules for oral administration are prepared as follows:

Ingredients Amount Compound of the Invention 8.2 mg Microcrystalline cellulose (Avicel PH 103) 139.05 mg Magnesium stearate 0.75 mg

-   -   Representative Procedure: The ingredients are thoroughly blended         and then loaded into a gelatin capsule (Size #1, White, Opaque)         (148 mg of composition per capsule).

It will be understood that any form of the compounds of the invention, (i.e. free base, pharmaceutical salt, or solvate) that is suitable for the particular mode of administration, can be used in the pharmaceutical compositions discussed above.

Utility

The benzimidazole-carboxamide compounds of the invention are 5-HT₄ receptor agonists and therefore are expected to be useful for treating medical conditions mediated by 5-HT₄ receptors or associated with 5-HT₄ receptor activity, i.e. medical conditions which are ameliorated by treatment with a 5-HT₄ receptor agonist. Such medical conditions include, but are not limited to, irritable bowel syndrome (IBS), chronic constipation, functional dyspepsia, delayed gastric emptying, gastroesophageal reflux disease (GERD), gastroparesis, post-operative ileus, intestinal pseudo-obstruction, and drug-induced delayed transit. In addition, it has been suggested that some 5-HT₄ receptor agonist compounds may be used in the treatment of central nervous system disorders including cognitive disorders, behavioral disorders, mood disorders, and disorders of control of autonomic function.

In particular, the compounds of the invention increase motility of the gastrointestinal (GD tract and thus are expected to be useful for treating disorders of the GI tract caused by reduced motility in mammals, including humans. Such GI motility disorders include, by way of illustration, chronic constipation, constipation-predominant irritable bowel syndrome (C-IBS), diabetic and idiopathic gastroparesis, and functional dyspepsia.

In one aspect, therefore, the invention provides a method of increasing motility of the gastrointestinal tract in a mammal, the method comprising administering to the mammal a therapeutically effective amount of a pharmaceutical composition comprising a pharmaceutically-acceptable carrier and a compound of the invention.

When used to treat disorders of reduced motility of the GI tract or other conditions mediated by 5-HT₄ receptors, the compounds of the invention will typically be administered orally in a single daily dose or in multiple doses per day, although other forms of administration may be used. The amount of active agent administered per dose or the total amount administered per day will typically be determined by a physician, in the light of the relevant circumstances, including the condition to be treated, the chosen route of administration, the actual compound administered and its relative activity, the age, weight, and response of the individual patient, the severity of the patient's symptoms, and the like.

Suitable doses for treating disorders of reduced motility of the GI tract or other disorders mediated by 5-HT₄ receptors will range from about 0.0007 to about 20 mg/kg/day of active agent, including from about 0.0007 to about 1 mg/kg/day. For an average 70 kg human, this would amount to from about 0.05 to about 70 mg per day of active agent.

In one aspect of the invention, the compounds of the invention are used to treat chronic constipation. When used to treat chronic constipation, the compounds of the invention will typically be administered orally in a single daily dose or in multiple doses per day. Preferably, the dose for treating chronic constipation will range from about 0.05 to about 70 mg per day.

In another aspect of the invention, the compounds of the invention are used to treat irritable bowel syndrome. When used to treat constipation-predominant irritable bowel syndrome, the compounds of the invention will typically be administered orally in a single daily dose or in multiple doses per day. Preferably, the dose for treating constipation-predominant irritable bowel syndrome will range from about 0.05 to about 70 mg per day.

In another aspect of the invention, the compounds of the invention are used to treat diabetic gastroparesis. When used to treat diabetic gastroparesis, the compounds of the invention will typically be administered orally in a single daily dose or in multiple doses per day. Preferably, the dose for treating diabetic gastroparesis will range from about 0.05 to about 70 mg per day.

In yet another aspect of the invention, the compounds of the invention are used to treat functional dyspepsia. When used to treat functional dyspepsia, the compounds of the invention will typically be administered orally in a single daily dose or in multiple doses per day. Preferably, the dose for treating functional dyspepsia will range from about 0.05 to about 70 mg per day.

The invention also provides a method of treating a mammal having a disease or condition associated with 5-HT₄ receptor activity, the method comprising administering to the mammal a therapeutically effective amount of a compound of the invention or of a pharmaceutical composition comprising a compound of the invention.

As described above, compounds of the invention are 5-HT₄ receptor agonists. The invention further provides, therefore, a method of agonizing a 5-HT₄ receptor in a mammal, the method comprising administering a compound of the invention to the mammal. In addition, the compounds of the invention are also useful as research tools for investigating or studying biological systems or samples having 5-HT₄ receptors, or for discovering new 5-HT₄ receptor agonists. Moreover, since compounds of the invention exhibit binding selectivity for 5-HT₄ receptors as compared with binding to receptors of other 5-HT subtypes, particularly 5-HT₃ receptors, such compounds are particularly useful for studying the effects of selective agonism of 5-HT₄ receptors in a biological system or sample. Any suitable biological system or sample having 5-HT₄ receptors may be employed in such studies which may be conducted either in vitro or in vivo. Representative biological systems or samples suitable for such studies include, but are not limited to, cells, cellular extracts, plasma membranes, tissue samples, mammals (such as mice, rats, guinea pigs, rabbits, dogs, pigs, etc.) and the like.

In this aspect of the invention, a biological system or sample comprising a 5-HT₄ receptor is contacted with a 5-HT₄ receptor-agonizing amount of a compound of the invention. The effects of agonizing the 5-HT₄ receptor are then determined using conventional procedures and equipment, such as radioligand binding assays and functional assays. Such functional assays include ligand-mediated changes in intracellular cyclic adenosine monophosphate (cAMP), ligand-mediated changes in activity of the enzyme adenylyl cyclase (which synthesizes cAMP), ligand-mediated changes in incorporation of analogs of guanosine triphosphate (GTP), such as [³⁵S]GTPγS (guanosine 5′-O-(γ-thio)triphosphate) or GTP-Eu, into isolated membranes via receptor catalyzed exchange of GTP analogs for GDP analogs, ligand-mediated changes in free intracellular calcium ions (measured, for example, with a fluorescence-linked imaging plate reader or FLIPR® from Molecular Devices, Inc.), and measurement of mitogen activated protein kinase (MAPK) activation. A compound of the invention may agonize or increase the activation of 5-HT₄ receptors in any of the functional assays listed above, or assays of a similar nature. A 5-HT₄ receptor-agonizing amount of a compound of the invention will typically range from about 1 nanomolar to about 500 nanomolar.

Additionally, the compounds of the invention can be used as research tools for discovering new 5-HT₄ receptor agonists. In this embodiment, 5-HT₄ receptor binding or functional data for a test compound or a group of test compounds is compared to the 5-HT₄ receptor binding or functional data for a compound of the invention to identify test compounds that have superior binding or functional activity, if any. This aspect of the invention includes, as separate embodiments, both the generation of comparison data (using the appropriate assays) and the analysis of the test data to identify test compounds of interest.

Among other properties, compounds of the invention have been found to be potent agonists of the 5-HT₄ receptor and to exhibit substantial selectivity for the 5-HT₄ receptor subtype over the 5-HT₃ receptor subtype in radioligand binding assays. Further, compounds of the invention of which particular mention was made have demonstrated superior pharmacokinetic properties in a rat model. Such compounds are thus expected to be highly bioavailable upon oral administration. In addition, these compounds have been shown not to exhibit an unacceptable level of inhibition of the potassium ion current in an in vitro voltage-clamp model using isolated whole cells expressing the hERG cardiac potassium channel. The voltage-clamp assay is an accepted pre-clinical method of assessing the potential for pharmaceutical agents to change the pattern of cardiac repolarization, specifically to cause, so-called QT prolongation, which has been associated with cardiac arrhythmia. (Cavero et al., Opinion on Pharmacotherapy, 2000, 1, 947-73, Fermini et al., Nature Reviews Drug Discovery, 2003, 2, 439-447) Accordingly, pharmaceutical compositions comprising compounds of the invention are expected to have an acceptable cardiac profile.

There properties, as well as the utility of the compounds of the invention, can be demonstrated using various in vitro and in vivo assays well-known to those skilled in the art. Representative assays are described in further detail in the following examples.

EXAMPLES

The following synthetic and biological examples are offered to illustrate the invention, and are not to be construed in any way as limiting the scope of the invention. In the examples below, the following abbreviations have the following meanings unless otherwise indicated. Abbreviations not defined below have their generally accepted meanings.

Boc=tert-butoxycarbonyl

DMSO=dimethyl sulfoxide

MeCN=acetonitrile

TFA=trifluoroacetic acid

R_(f)=retention factor

Reagents and solvents were purchased from commercial suppliers (Aldrich, Fluka, Sigma, etc.), and used without further purification. Reactions were run under nitrogen atmosphere, unless noted otherwise. Progress of reaction mixtures was monitored by thin layer chromatography (TLC), analytical high performance liquid chromatography (anal. HPLC), and mass spectrometry, the details of which are given below and separately in specific examples of reactions. Reaction mixtures were worked up as described specifically in each reaction; commonly they were purified by extraction and other purification methods such as temperature-, and solvent-dependent crystallization, and precipitation. In addition, reaction mixtures were routinely purified by preparative HPLC: a general protocol is described below. Characterization of reaction products was routinely carried out by mass and ¹H-NMR spectrometry. For NMR measurement, samples were dissolved in deuterated solvent (CD₃OD, CDCl₃, or DMSO-d₆), and ¹H-NMR spectra were acquired with a Varian Gemini 2000 instrument (300 MHz) under standard observation conditions. Mass spectrometric identification of compounds was performed by an electrospray ionization method (ESMS) with an Applied Biosystems (Foster City, Calif.) model API 150 EX instrument or an Agilent (Palo Alto, Calif.) model 1100 LC/MSD instrument.

Preparation 1: Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide a. Preparation of 2,3-diaminobenzoic acid methyl ester

To a nitrogen-saturated solution of 2-amino-3-nitrobenzoic acid methyl ester (Chess GmbH, 50 g, 0.26 mol) in absolute ethanol (800 mL) was added palladium hydroxide (Degussa, 20% w/w on carbon, 58.75% w/w water, 10 g). The slurry was degassed then shaken vigorously under hydrogen (4 atm) at room temperature for 48 h. The catalyst was filtered and the filtrate concentrated in vacuo to afford 2,3-diaminobenzoic acid methyl ester as a dark orange oil that solidified on standing (43 g, 0.26 mol, 100%). (m/z): [M-OCH₃]⁺ calcd for C₈H₁₀N₂O₂ 135.05. found 135.3. ¹H NMR (300 MHz, DMSO-d₆):

(ppm) 3.74 (s, 3H), 4.80 (br s, 1H), 6.20 (br s, 1H), 6.38 (t, 1H), 6.70 (d, 1H), 7.06 (d, 1H).

b. Preparation of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid

A slurry of 2,3-diaminobenzoic acid methyl ester (21.5 g, 0.13 mol) and isobutyric acid (36.2 mL, 0.39 mol) in aqueous hydrochloric acid (4M, 210 mL) was stirred under reflux for 24 h to afford a homogenous solution. The solution was cooled to 10° C. and the pH raised to 3.5 using aqueous sodium hydroxide solution (4M, approx. 210 mL), while maintaining the temperature below 30° C. The reaction mixture was stirred at room temperature for 2 h, cooled to 10° C., and the resultant precipitate filtered off. The solid cake was transferred to a beaker and acetonitrile (300 mL) was added. The slurry was stirred at room temperature for 1 h then and filtered to afford a grey solid. The solid was dried under vacuum to afford the title intermediate (23 g, 0.11 mol, 87%). (m/z): [M+H]⁺ calcd for C₁₁H₁₂N₂O₂ calcd. 205.09. found 205.3. ¹H NMR (300 MHz, DMSO-d₆):

(ppm) 1.27 (d, 6H), 3.39 (m, 1H), 7.29 (t, 1H), 7.78 (m, 2H).

c. Preparation of 4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidine-1-carboxylic acid tert-butyl ester

To a solution of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (9.0 g, 44.1 mmol) in anhydrous N,N-dimethylformamide (100 mL) was added 4-aminomethyl-piperidine-1-carboxylic acid tert-butyl ester (9.4 g, 44.1 mmol), followed by N,N-diisopropylethylamine (16.9 mL, 97.0 mmol). The solution was stirred for 15 min at room temperature prior to the addition of hydroxybenzotriazole (5.9 g, 44.1 mmol), N-Ethyl-N-(3-dimethylaminopropyl)carbodiimide hydrochloride (8.4 g, 44.1 mmol), and additional N,N-dimethylformamide (50 mL). The reaction mixture was stirred at room temperature for 16 h, diluted with dichloromethane (300 mL), and washed sequentially with 1M aqueous phosphoric acid, 1M aqueous sodium hydroxide and brine. The solution was then dried over sodium sulfate and concentrated in vacuo to afford a brown oil which solidified upon addition of hexanes. The solid was filtered to give the title intermediate as a beige solid (13.8 g, 36.0 mmol, 78%). (m/z): [M+H]⁺ calcd for C₂₂H₃₂N₄O₃ 401.26. found 401.5; [M-Boc+H]⁺ 301.5. Retention time (anal. HPLC: 2-90% MeCN/H₂O over 6 min)=3.7 min. ¹H NMR (300 MHz, DMSO-d_(o)): δ (ppm) 1.20 (m, 2H), 1.37 (s, 9H), 1.37 (s, 6H), 1.72 (m, 1H), 1.75 (m, 2H), 2.73 (br s, 2H), 3.22 (septet, 1H), 3.36 (m, 2H), 3.95 (m, 2H), 7.26 (t, 1H), 7.63 (d, 1H), 7.79 (d, 1H), 10.11 (t, 1H).

d. Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide

To a solution of 4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidine-1-carboxylic acid tert-butyl ester (10.8 g, 27.0 mmol) dissolved in dichloromethane (50 mL) at 0° C. was slowly added trifluoroacetic acid (50 mL) in 5 mL portions. The solution was allowed to warm to room temperature, stirred for an additional 20 minutes then evaporated in vacuo. Excess trifluoroacetic acid was removed by co-evaporation with toluene. The residue was then dissolved in a minimal volume of dichloromethane and slowly added to diethyl ether (1 L) at 0° C. The resulting slurry was stirred for 2 h at room temperature then filtered to afford the bis-trifluoroacetate salt of the title compound as a light brown solid (12.7 g, 24.0 mmol, 89%). (m/z): [M+H]⁺ calcd for C₁₇H₂₄N₄O 301.21. found 301.5. Retention time (anal. HPLC: 2-50% MeCN/H₂O over 6 min)=1.65 min. ¹H NMR (300 MHz, MeOD-d₃): δ (ppm) 1.59 (d, 6H), 1.60 (m, 1H), 2.03 (m, 2H), 2.04 (m, 1H), 3.00 (m, 2H), 3.43 (m, 2H), 3.45 (m, 2H), 3.63 (septet, 1H), 7.63 (t, 1H), 7.90 (d, 1H), 7.96 (d, 1H), 9.04 (t, 1H).

Preparation 2: Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide a. Preparation of 4-(4-({[2-isopropyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidin-1-ylmethyl)piperidine-1-carboxylic acid tert-butyl ester

To a suspension of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide bis-trifluoroacetate (6.84 g, 12.95 mmol) in dichloromethane (65 mL) at room temperature under nitrogen was added sequentially N,N-diisopropylethylamine (1.67 g, 2.25 mL), a solution of 1-(tert-butoxycarbonyl)piperidine-4-carboxaldehyde (3.16 g, 14.89 mmol) in dichloromethane (5 mL) and sodium triacetoxyborohydride (3.84 g, 18.13 mmol). The resulting mixture was stirred at room temperature for 1.5 h, then acidified to pH 1 with 1M aqueous hydrochloric acid. The aqueous layer was removed, and the organic layer extracted with 1M aqueous hydrochloric acid until no product remained in the organic phase. The combined aqueous layers were washed with dichloromethane, cooled to 0° C. and basified to pH 12 with sodium hydroxide pellets. The solution was then extracted with dichloromethane until no product remained in the aqueous phase, and the combined organic layers washed with brine, dried over sodium sulfate, filtered and concentrated to give the desired product as a brown oil (5.4 g, 10.8 mmol, 84%) which was used without further purification. (m/z): [M+H]⁺ calcd for C₂₈H₄₃N₅O₃ 498.35. found 498.5.

b. Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide

The product of the previous step (5.4 g, 10.8 mmol) was dissolved in dichloromethane (40 mL) and cooled to 0° C. Trifluoroacetic acid (30 mL) was added, and the solution was stirred at 0° C. for a further 0.5 h. The mixture was then concentrated and co-evaporated twice with dichloromethane in vacuo. The resulting residue was dissolved in dichloromethane (20 mL), cooled to 0° C. and basified with 20% w/w aqueous sodium hydroxide (50 mL). The solution was allowed to warm to room temperature over 10 minutes, then filtered. The solid was rinsed with acetonitrile and dried in vacuo to afford a light gray powder (3.09 g, 7.8 mmol, 72%) which was used without further purification. (m/z): [M+H]⁺ calcd for C₂₃H₃₅N₅O 398.29. found 398.4.

Preparation 3: Synthesis of 2-tert-butyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide a. Preparation of 2-amino-3-(2,2-dimethylpropionylamino)benzoic acid methyl ester

To a solution of 2,3-diaminobenzoic acid methyl ester (2.3 g, 13.8 mmol) in pyridine (40 mL) at room temperature was added 2,2-dimethylpropionyl chloride (1.7 g, 14.0 mmol). The solution was stirred at for 16 h, evaporated, and the residue partitioned between ethyl acetate (100 mL) and 1M aqueous hydrochloric acid (100 mL). The organic phase was separated, washed with 1M aqueous hydrochloric acid (100 mL), dried over sodium sulfate and evaporated to afford the title compound as a dark oil (2.7 g, 10.8 mmol, 78%) which was used without further purification. (m/z): [M+H]⁺ calcd for C₁₃H₁₈N₂O₃ 251.14. found 250.8

b. Preparation of 2-tert-butyl-1H-benzoimidazole-4-carboxylic acid

A slurry of the product of the previous step (2.7 g, 10.8 mmol) in 4M aqueous hydrochloric acid (100 mL) was stirred under reflux for 24 h to afford a homogenous solution. The solvent was evaporated to afford the hydrochloride salt of the title intermediate as a brick-red solid (2.5 g, 9.8 mmol, 91%). (m/z): [M+H]⁺ calcd for C₁₂H₁₄N₂O₂ 219.12. found 219.3. ¹H NMR (300 MHz, DMSO-d₆):

(ppm) 1.45 (d, 9H), 3.39 (m, 1H), 7.91 (d, 1H), 7.95 (d, 1H).

c. Preparation of 4-{[(2-tert-butyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidine-1-carboxylic acid tert-butyl ester

To a solution of 2-tert-butyl-1H-benzoimidazole-4-carboxylic acid hydrochloride (1.11 g, 4.37 mmol) in anhydrous N,N-dimethylformamide (5 mL) was added 1,1′-carbonyldiimidazole (0.77 g, 4.75 mmol). The solution was stirred at 50° C. for 2 h, then 4-aminomethyl-piperidine-1-carboxylic acid tert-butyl ester (0.94 g, 4.39 mmol) was added, followed by 1,4-diazabicyclo[2,2,2]octane (1.46 g, 13 mmol). The solution was stirred at 50° C. for 16 h, allowed to cool and diluted with water (20 mL) and ethyl acetate (60 mL). The aqueous layer was removed, the organic layer washed with water (20 mL), dried over sodium sulfate and concentrated in vacuo to afford the title intermediate (1.32 g, 3.18 mmol, 73%) which was used without further purification. (m/z): [M+H]⁺ calcd for C₂₃H₃₄N₄O₃ 415.27. found 415.5.

d. Preparation of 2-tert-butyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide

4-{[(2-tert-Butyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidine-1-carboxylic acid tert-butyl ester (13.5 g, 32.6 mmol) was dissolved in 4N HCl in dioxane (200 mL) and stirred at room temperature for 0.5 h. The resulting solid was filtered to afford the bis hydrochloride salt of the title intermediate (11.3 g, 29.3 mmol, 89%).

(m/z): [M+H]⁺ calcd for C₁₈H₂₆N₄O 315.22. found 315.3. ¹H NMR (300 MHz, D₂O+MeOD-d₃): 1.54 (s, 8H), 1.96 (m, 4H), 2.91 (m, 4H), 3.31 (br s, 1H), 3.45 (d, 2H), 7.56 (t, 1H), 7.89-7.92 (m, 2H)

e. Preparation of 4-(4-{[(2-tert-butyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidin-1-ylmethyl)piperidine-1-carboxylic acid tert-butyl ester

To a suspension of the bis HCl salt of 2-tert-butyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide (4.28 g, 11.06 mmol) in dichloromethane (55 mL) at room temperature was added N,N-diisopropylethylamine (1.71 g, 2.31 mL), 1-(tert-butoxycarbonyl)piperidine-4-carboxaldehyde (2.58 g, 12.17 mmol) and sodium triacetoxyborohydride (3.28 g, 15.48 mmol) sequentially. The resulting mixture was stirred at room temperature for 2 h then extracted with 1M aqueous hydrochloric acid. The combined aqueous layers were basified to pH 12 with sodium hydroxide pellets, then extracted with dichloromethane. The combined organic layers were dried over sodium sulfate, filtered and evaporated. The resulting residue was dried under high vacuum to give a light brownish foam (4.9 g, 9.6 mmol, 87%) which was used without further purification. (m/z): [M+H]⁺ calcd for C₂₉H₄₅N₅O₃ 512.35. found: 512.4.

f. Synthesis of 2-tert-butyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide

Crude 4-(4-{[(2-tert-butyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidin-1-ylmethyl)piperidine-1-carboxylic acid tert-butyl ester, prepared as in the previous step (5.1 g, 10 mmol) was treated with a mixture of trifluoroacetic acid (40 mL) and dichloromethane (40 mL) at room temperature for 0.5 h. The mixture was concentrated in vacuo, redissolved in dichloromethane (25 mL) and basified with 1M aqueous sodium hydroxide (15 mL). The organic layer was removed, and the aqueous layer re-extracted with dichloromethane. The combined organic phases were dried over sodium sulfate, filtered, and concentrated in vacuo to afford the desired product as a brown foam (3.6 g, 8.8 mmol, 88%). (m/z): [M+H]⁺ calcd for C₂₄H₃₇N₅O 412.31. found 412.6.

Preparation 4. Synthesis of 4-(4-aminomethylpiperidin-1-ylmethyl)-piperidine-1-carboxylic acid methyl ester a. Preparation of 4-[4-(tert-butoxycarbonylamino-methyl)piperidin-1-ylmethyl]-piperidine-1-carboxylic acid methyl ester

To a solution of 4-tert-butoxycarbonylaminomethylpiperidine (3.62 g, 16.9 mmol) in dichloromethane (100 mL) was added 4-formylpiperidine-1-carboxylic acid methyl ester (2.89 g, 16.9 mmol) and acetic acid (0.96 mL). The mixture was stirred at room temperature for 10 min prior to the addition of sodium triacetoxyborohydride (5.4 g, 25.5 mmol). The final mixture was stirred at room temperature for 1 h. The reaction was terminated by adding saturated sodium bicarbonate solution (50 mL). The mixture was extracted with dichloromethane (100 mL), and the organic layer was dried over MgSO₄. Evaporation of the organic solution afforded a pale yellow oily residue. It was purified by flash silica column chromatography (CH₂Cl₂ to 5% MeOH/CH₂Cl₂), yielding the title intermediate (4.4 g). (m/z): [M+H]⁺ calcd for C₁₉H₃₅N₃O₄ 370.27. found 370.5.

b. Synthesis of 4-(4-aminomethylpiperidin-1-ylmethyl)-piperidine-1-carboxylic acid methyl ester

To a solution of 4-[4-(tert-butoxycarbonylamino-methyl)piperidin-1-ylmethyl]-piperidine-1-carboxylic acid methyl ester (4.4 g, 10.8 mmol) in dichloromethane (20 mL) was added trifluoroacetic acid (20 mL). After stirring for 20 min at room temperature, the solution was evaporated in vacuo, yielding the bis-trifluoroacetate salt of the title compound as a pale yellow oil, which was used without further treatment. (m/z): [M+H]⁺ calcd for C₁₄H₂₇N₃O₂ 270.22. found 270.5. ¹H-NMR (CD₃OD) δ (ppm) 4.0 (br d, 2H), 3.6 (m, 5H), 2.9-2.7 (m, 6H), 2.1-1.9 (m, 2H), 1.7-1.5 (m, 6H), 1.2-1.0 (m, 4H).

Example 1 Synthesis of 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester

To a suspension of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide (2.9 g, 7.3 mmol) in dichloromethane (50 mL) was added N,N-diisopropylethylamine (1.05 mL, 7.3 mmol). The resulting solution was cooled to 0° C., and methyl chloroformate (576 μL, 7.3 mmol) was added dropwise. The mixture was stirred at 0° C. for 1.5 h, quenched with acetic acid (1 mL) and evaporated in vacuo to afford a beige solid (4.8 g) which was purified via preparative reverse phase HPLC [gradient of 5-10-25% (5-10% over 10 min; 10-25% over 50 min); flow rate 15 mL/min; detection at 280 nm] to afford the bis trifluoroacetate salt of the title compound as a white solid (3.5 g, 5.1 mmol, 70%). (m/z): [M+H]⁺ calcd for C₂₅H₃₇N₅O₃ 456.30. found 456.3. Retention time (anal. HPLC: 2-50% MeCN/H₂O over 6 min)=3.06 min.

Example 2 Synthesis of 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]-methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid phenyl ester

To a solution of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide (0.22 g, 0.55 mmol) and N,N-diisopropylethylamine (0.19 mL) in dichloromethane (5.0 mL) was added phenyl chloroformate (70 μL). The mixture was stirred at room temperature for 10 min, then concentrated in vacuo and purified via preparative reverse phase HPLC to afford the bis trifluoroacetate salt of the title compound as a white solid (98.4 mg, 0.13 mmol, 24%). (m/z): [M+H]⁺ calcd for C₃₀H₃₉N₅O₃ 518.32. found 518.6. ¹H NMR (300 MHz, MeOD-d₃): δ (ppm) 1.14-1.28 (m, 2H), 1.39-1.53 (m, 6H), 1.52-1.62 (m, 2H), 1.70-1.78 (m, 2H), 1.92-2.06 (m, 4H), 2.82-2.97 (m, 6H), 3.32-3.38 (m, 2H), 3.43-3.50 (m, 1H), 3.52-3.69 (m, 2H), 4.04-4.12 (m, 1H), 4.18-4.26 (m, 1H), 6.91-6.98 (m, 1H), 7.08-7.13 (m, 1H), 7.21-7.28 (m, 1H), 7.45-7.50 (m, 1H), 7.73-7.77 (m, 1H), 7.81-7.87 (m, 1H), 9.02-9.32 (brs, 1H).

Example 3 Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(2-chlorobenzoyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide

To a suspension of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide (2.1 g, 5.29 mmol) in tetrahydrofuran (26 mL) at room temperature was added N,N-diisopropylethylamine (2.05 g, 15.87 mmol), dichloromethane (12 mL) and N,N-dimethylformamide (5 mL). To the resulting suspension was slowly added o-chlorobenzoyl chloride (1.02 g, 5.82 mmol), and the reaction mixture was stirred for 0.5 h at room temperature. The solution was concentrated in vacuo, the resulting residue diluted with acetic acid (7.5 mL) and water (0.5 mL), and the product purified by reverse phase preparative HPLC. The purified salt was partitioned between dichloromethane and 1M aqueous sodium hydroxide, the organic layer removed and the aqueous layer re-extracted with dichloromethane, and the combined organic layers washed with brine, dried over sodium sulfate and concentrated in vacuo to give the title compound as a white foam (1.75 g, 3.26 mmol, 62%).

(m/z): [M+H]⁺ calcd for C₃₀H₃₈ClN₅O₂) 536.28. found 536.3. ¹H NMR (300 MHz, DMSO-d₆): 0.90 (br m, 2H), 1.24 (d, 6H), 1.45 (br m, 2H), 1.68 (br m, 8H), 1.96 (m, 1H), 2.72 (br m, 5H), 3.08 (m, 2H), (3.20, m, 3H), 4.40 (br m, 1H), 7.14 (t, 1H), 7.28 (m, 2H), 7.39 (m, 1H), 7.49 (dd, 1H), 7.66 (dd, 1H).

Examples 4-6

Using processes similar to that of Example 3, except replacing the o-chlorobenzoyl chloride with the appropriate chloride reagent, the compounds of Examples 4-6 were prepared.

Example 4

2-isopropyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(2,4-difluoro-benzoyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; (m/z): [M+H]⁺ calcd for C₃₀H₃₇F₂N₅O₂, 538.30. found 538.2. Retention time (anal. HPLC: 2-60% MeCN/H₂O over 4 min)=2.12 min. ¹H NMR (300 MHz, DMSO-d₆): 0.92 (m, 2H), 1.30 (m, 2H), 1.38 (d, 6H), 1.53 (m, 2H), 1.60-1.90 (m, 6H), 2.07 (d, 2H), 2.73-2.85 (br m, 3H), 3.05 (t, 1H), 3.22 (septet, 1H), 3.38 (br m, 3H), 4.44 (br d, 1H), 7.10-7.50 (m, 4H), 7.62 (d, 1H), 7.77 (d, 1H), 10.10 (br s, 1H).

Example 5

2-isopropyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(furan-2-carbonyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; (m/z): [M+H]⁺ calcd for C₂₈H₃₇N₅O₃ 492.30. found 492.2. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=1.68 min.

Example 6

2-isopropyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(thiophene-2-carbonyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; (m/z): [M+H]⁺ calcd for C₂₈H₃₇N₅O₂S 508.28. found 508.2. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=1.94 min.

Example 7 Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(2-fluoro-5-trifluoromethylbenzoylpiperidin-4-ylmethyl]piperidin-4-ylmethyl}amide

To a solution of 2-fluoro-5-trifluoromethyl benzoic acid (100 mg, 0.48 mmol) in dimethylformamide (4 mL) at room temperature was added O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (200 mg, 0.48 mmol). The mixture was stirred at room temperature for 0.25 h, then 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide (210 mg, 0.48 mmol) and N,N-diisopropylethylamine (0.184 mL, 0.96 mmol) were added and stirring continued for a further 0.5 h. The solution was evaporated in vacuo and the crude product purified by reverse phase HPLC [gradient of 5-10-25% (5-10% over 10 min; 10-25% over 50 min); flow rate 15 mL/min; detection at 280 nm] to afford the his trifluoroacetate salt of the title compound as a white solid (70 mg, 0.09 mmol, 18%). (m/z): [M+H]⁺ calcd for C₃₁H₃₇F₄N₅O₂ 588.30. found 588.2. Retention time (anal. HPLC: 2-60% MeCN/H₂O over 4 min)=2.39 min.

Example 8 Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(2-fluoro-phenylcarbamoyl)piperidin-4-ylmethyl]piperidin-4-ylmethyl}-amide

2-Isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide (220 mg, 0.55 mmol) was dissolved in N,N-dimethylformamide (2.0 mL) at room temperature. To this solution was added N,N-diisopropylethylamine (143.2 mg, 1.1 mmol) followed by o-fluorophenylisocyanate (75.4 mg, 0.55 mmol). The resulting mixture was stirred at room temperature overnight, concentrated in vacuo and the residue purified by preparative reverse-phase HPLC to afford the bis trifluoroacetate salt of the title compound as a white solid (92.6 mg, 0.12 mmol, 22%). (m/z): [M+H]⁺ calcd for C₃₀H₃₉FN₆O₂ 535.32. found 535.2. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=2.09 min.

Example 9 Synthesis of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid [1-(1-methanesulfonylpiperidin-4-ylmethyl)piperidin-4-ylmethyl]amide

2-Isopropyl-1H-benzoimidazole-4-carboxylic acid (1-piperidin-4-ylmethylpiperidin-4-ylmethyl)amide (40 mg, 0.1 mmol) was dissolved in N,N-dimethylformamide (1.0 mL) at room temperature. To this solution was added N,N-diisopropylethylamine (0.175 mL, 1 mmol) followed by methanesulfonyl chloride (11.5 mg, 0.1 mmol). The mixture was stirred at room temperature for 16 h, then concentrated in vacuo and the residue purified by preparative reverse-phase HPLC to afford the his trifluoroacetate salt of the title compound as a white solid (27.2 mg, 0.04 mmol, 40%). (m/z): [M+H]⁺ calcd for C₂₄H₃₇N₅O₃S 476.27. found 476.2. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=1.66 min.

Example 10 Synthesis of 4-(4-{[(2-tert-butyl-1H-benzoimidazole-4-carbonyl)-amino]-methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester

To the crude product of Preparation 3 (2.4 g, 5.8 mmol) in dichloromethane (29 mL) at room temperature was added N,N-diisopropylethylamine (1.5 g, 11.6 mmol). The resulting mixture was cooled to 0° C. and methyl chloroformate (660 mg, 6.98 mmol) was added dropwise. The reaction was allowed to warm to room temperature and stirred for a further 10 min. The solution was concentrated, re-dissolved in 50% acetic acid in water, filtered and purified by reversed phase preparative HPLC. The resulting solid was dissolved in dichloromethane and washed with 1M aqueous sodium hydroxide. The aqueous layer was extracted twice with dichloromethane, and the combined organic layers washed with brine, dried over sodium sulfate, filtered and concentrated to give the title compound as a white foam (1.3 g, 2.8 mmol, 48%). (m/z): [M+H]⁺ calcd for C₂₆H₃₉N₅O₃ 470.32. found 470.6. ¹H NMR (300 MHz, MeOD-d₃): 6 (ppm) 1.02-1.16 (m, 2H), 1.49 (s, 9H), 1.47-1.7 (m, 4H), 1.82-2.03 (m, 4H), 2.74-2.94 (m, 6H), 3.31-3.40 (m, 2H), 3.54-3.58 (m, 2H), 3.56 (s, 3H), 3.98-4.03 (m, 2H), 7.41-7.46 (m, 1H), 7.71-7.74 (m, 1H), 7.79-7.82 (m, 1H), 9.35 (brs, 1H).

Examples 11-13

Using processes similar to that of Example 10, except replacing the methyl chloroformate with the appropriate chloride reagent, the compounds of Examples 11-13 were prepared.

Example 11

2-tert-butyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(2-fluoro-benzoyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; (m/z): [M+H]⁺ calcd for C₃₁H₄₀FN₅O₂ 534.33. found 534.4. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=2.09 min.

Example 12

2-tert-butyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(3-methyl-benzoyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; (m/z): [M+H]⁺ calcd for C₃₂H₄₃N₅O₂ 530.35. found 530.42. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=2.22.

Example 13

2-tert-butyl-1H-benzoimidazole-4-carboxylic acid {1-[1-(4-fluorobenzoyl)-piperidin-4-ylmethyl]piperidin-4-ylmethyl}amide; (m/z): [M+H]⁺ calcd for C₃₁H₄₀FN₅O₂ 534.33. found 534.4. Retention time (anal. HPLC: 2-65% MeCN/H₂O over 4 min)=2.17.

Example 14 Synthesis of 4-[4-({[2-(1-hydroxy-1-methylethyl)-1H-benzoimidazole-4-carbonyl]amino}methyl)piperidin-1-ylmethyl]piperidine-1-carboxylic acid methyl ester a. Preparation of 2-(1-hydroxy-1-methylethyl)-1H-benzoimidazole-4-carboxylic acid

To a solution of 2,3-diaminobenzoic acid methyl ester (1.5 g, 9.2 mmol) in 4 M HCl (50 mL) was added 2-hydroxyisobutyric acid (2.87 g, 27.6 mmol). The mixture was stirred at ˜90° C. for 24 h. It was neutralized by use of aqueous sodium hydroxide solution to pH˜3, and concentrated to dryness. The residue was suspended in methanol, and filtered through a filter paper. The filtrate was concentrated and the residue was rinsed with ether. The remaining solid residue was dissolved in ethyl acetate, and washed with brine solution. After drying over MgSO₄, the organic solution was evaporated in vacuo, yielding the title intermediate as a pale yellow oil (˜800 mg). The crude product was used in the next step without further purification. (m/z): [M+H]⁺ calcd for C₁₁H₁₂N₂O₃ 221.09. found 221.1. ¹H-NMR (CD₃OD) δ (ppm) 7.8 (dd, 1H), 7.7 (dd, 1H), 7.2 (m, 1H), 1.3 (s, 6H).

b. Synthesis of 4-[4-({[2-(1-hydroxy-1-methylethyl)-1H-benzoimidazole-4-carbonyl]amino}methyl)piperidin-1-ylmethyl]piperidine-1-carboxylic acid methyl ester

To a solution of the benzoimidazole carboxylic acid product of the previous step (0.7 g, 3.18 mmol), the aminomethylpiperidine product of Preparation 4 as the bis-TFA salt (1.2 g, 3.13 mmol), and hydroxybenzotriazole (HOBt) (0.43 g, 3.18 mmol) in dimethylformamide (50 mL) was added triethylamine (1.3 mL, 9.3 mmol) and N-Ethyl-N′-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) (0.67 g, 3.5 mmol). The mixture was stirred at room temperature for 12 h, and concentrated to dryness in vacuo. The residue was partitioned between dichloromethane (150 mL) and saturated sodium bicarbonate. The organic layer was dried over MgSO₄, and evaporated to dryness, yielding a pale yellow oily residue. It was purified by preparative HPLC to provide the bis-trifluoroacetate salt of the title compound. (m/z): [M+H]⁺ calcd for C₂₅H₃₇N₅O₄ 472.29. found 472.5. Retention time (anal. HPLC: 5-30% MeCN/H₂O over 6 min)=3.67 min. ¹H-NMR (CD₃OD) δ (ppm) 7.9-7.8 (m, 2H), 7.6-7.5 (t, 1H), 4.0 (br d, 2H), 3.6 (s, 5H), 2.9-2.75 (br m, 5H), 2.05-1.9 (br d, 3H), 1.68 (m, 6H), 1.15 (m, 4H).

Example 15 Synthesis of 4-[4-({[2-(2-hydroxy-1-methylethyl)-1H-benzoimidazole-4-carbonyl]amino}methyl)-piperidin-1-ylmethyl]piperidine-1-carboxylic acid methyl ester a. Preparation of 2-(2-hydroxy-1-methylethyl)-1H-benzoimidazole-4-carboxylic acid

To a solution of 2,3-diaminobenzoic acid methyl ester (2.1 g, 14.1 mmol) in 4 M HCl (90 mL) was added 2-methyl-3-hydroxypropionic acid methyl ester (5 g, 42.3 mmol). The mixture was stirred at ˜90° C. for 24 h. It was neutralized by use of aqueous sodium hydroxide solution to pH˜3, and concentrated to dryness. The residue was suspended in methanol, and filtered through a filter paper. After the filtrate was concentrated, the remaining solid residue was dissolved in water and washed with ethyl acetate. The aqueous solution was evaporated in vacuo yielding the title intermediate as a pale yellow oil (˜800 mg). The crude product was used in the next step without further purification. (m/z): [M+H]⁺ calcd for C₁₁H₁₂N₂O₃ 221.09. found 221.3. ¹H-NMR (CD₃OD) δ (ppm) 8.1 (d, 1H), 7.9 (m, 1H), 7.6 (t, 1H), 3.8 (m, 2H), 3.6 (m, 1H), 1.4 (d, 3H).

b. Synthesis of 4-[4-({[2-(2-hydroxy-1-methylethyl)-1H-benzoimidazole-4-carbonyl]amino}methyl)piperidin-1-ylmethyl]piperidine-1-carboxylic acid methyl ester

To a solution of the benzoimidazole carboxylic acid product of the previous step (0.45 g, 1.75 mmol), the aminomethylpiperidine product of Preparation 4 as the bis-trifluoroacetate salt (0.8 g, 1.6 mmol), and HOBt (0.237 g, 1.75 mmol) in dimethylformamide (50 mL) was added triethylamine (0.98 mL, 7.0 mmol) and EDC (0.353 g, 1.84 mmol). The mixture was stirred at room temperature for 12 h, and concentrated to dryness under reduced pressure. The residue was partitioned between dichloromethane (150 mL) and saturated sodium bicarbonate. The organic layer was dried over MgSO₄, and evaporated to dryness, yielding pale yellow oily residue. It was purified by preparative HPLC, yielding the bis-trifluoroacetate salt of the title compound (0.2 g).

(m/z): [M+H]⁺ calcd for C₂₅H₃₇N₅O₄ 472.29. found 472.5. Retention time (anal. HPLC: 10-40% MeCN/H₂O over 6 min)=3.31 min. ¹H-NMR (CD₃OD) 8 (ppm) 7.9-7.8 (m, 2H), 7.6-7.5 (m, 1H), 4.0 (br d, 2H), 3.85-3.7 (m, 2H), 3.6 (br s, 6H), 3.3 (br, 2H), 2.9-2.6 (br m, 6H), 2.0-1.8 (br, 4H), 1.7-1.5 (m, 6H), 1.4 (m, 3H), 1.1-1.0 (m, 4H).

Additional Compounds of the Invention

Using the procedures of Examples 1-13 and variations thereof, the compounds of Tables I to IX were prepared and characterized by mass spectrometry. In the following tables, blank entries denote hydrogen.

TABLE I

Example Molecular [M + H]⁺ [M + H]⁺ No. R¹ R² Formula calcd found 16 iPr —CH₂-phenyl C₃₁H₄₁N₅O₃ 532.32 532.2 17 iPr iPr C₂₇H₄₁N₅O₃ 484.32 484.2 18 tBu phenyl C₃₁H₄₁N₅O₃ 532.32 532.2 19 tBu —CH₂-phenyl C₃₂H₄₃N₅O₃ 546.34 546.4 20 tBu iPr C₂₈H₄₃N₅O₃ 498.34 498.4

TABLE II

Example Molecular [M + H]⁺ [M + H]⁺ No. R¹ R^(3a) R^(3b) R^(3c) R^(3d) R^(3e) Formula calcd found 21 tBu Cl C₃₁H₄₀ClN₅O₂ 550.29 550.6 22 iPr C₃₀H₃₉N₅O₂ 502.31 502.4 23 iPr F C₃₀H₃₈FN₅O₂ 520.30 520.2 24 iPr CH₃ C₃₁H₄₁N₅O₂ 516.33 516.4 25 iPr CF₃ C₃₁H₃₈F₃N₅O₂ 570.30 570.2 26 iPr F C₃₀H₃₈FN₅O₂ 520.30 520.2 27 iPr CH₃ C₃₁H₄₁N₅O₂ 516.33 516.4 28 iPr CF₃ C₃₁H₃₈F₃N₅O₂ 570.30 570.2 29 iPr Cl C₃₀H₃₈ClN₅O₂ 536.27 536.2 30 iPr CF₃ C₃₁H₃₈F₃N₅O₂ 570.30 570.2 31 iPr CH₃ C₃₁H₄₁N₅O₂ 516.33 516.4 32 iPr Cl C₃₀H₃₈ClN₅O₂ 536.27 536.2 33 iPr OCH₃ C₃₁H₄₁N₅O₃ 532.32 532.2 34 iPr F C₃₀H₃₈FN₅O₂ 520.30 520.2 35 iPr F F C₃₀H₃₇F₂N₅O₂ 538.29 538.2 36 iPr F F C₃₀H₃₇F₂N₅O₂ 538.29 538.2 37 iPr F F C₃₀H₃₇F₂N₅O₂ 538.29 538.2 38 iPr F F C₃₀H₃₇F₂N₅O₂ 538.29 538.2 39 iPr F F C₃₀H₃₇F₂N₅O₂ 538.29 538.2 40 iPr F Cl C₃₀H₃₇ClFN₅O₂ 554.26 554.4 41 iPr CF₃ CF₃ C₃₂H₃₇F₆N₅O₂ 638.29 638.2 42 iPr Cl F C₃₀H₃₇ClFN₅O₂ 554.26 554.2 43 iPr Cl Cl C₃₀H₃₇Cl₂N₅O₂ 570.23 570.2 44 iPr OCF₃ C₃₁H₃₈F₃N₅O₃ 586.29 586.2 45 iPr CF₃ F C₃₁H₃₇F₄N₅O₂ 588.29 588.2 46 iPr Cl F C₃₀H₃₇ClFN₅O₂ 554.26 554.2 47 iPr OCH₃ Cl C₃₁H₄₀ClN₅O₃ 566.28 566.2 48 iPr CN C₃₁H₃₈N₆O₂ 527.31 527.2 49 iPr Cl Cl C₃₀H₃₇Cl₂N₅O₂ 570.23 570.2 50 iPr F CF₃ C₃₁H₃₇F₄N₅O₂ 588.29 588.2 51 iPr CN C₃₁H₃₈N₆O₂ 527.31 527.2 52 iPr OCHF₂ C₃₁H₃₉F₂N₅O₃ 568.30 568.8 53 tBu Cl F C₃₁H₃₉ClFN₅O₂ 568.28 568.2 54 tBu Cl Cl C₃₁H₃₉Cl₂N₅O₂ 584.25 584.2 55 tBu CN C₃₂H₄₀N₆O₂ 541.32 541.4 56 tBu OCF₃ C₃₂H₄₀F₃N₅O₃ 600.31 600.2 57 tBu CF₃ F C₃₂H₃₉F₄N₅O₂ 602.30 602.2 58 tBu Cl F C₃₁H₃₉ClFN₅O₂ 568.28 568.2 59 tBu OCH₃ Cl C₃₂H₄₂ClN₅O₃ 580.30 580.2 60 tBu CN C₃₂H₄₀N₆O₂ 541.32 541.4 61 tBu Cl Cl C₃₁H₃₉Cl₂N₅O₂ 584.25 584.2 62 tBu F CF₃ C₃₂H₃₉F₄N₅O₂ 602.30 602.2 63 tBu F CF₃ C₃₂H₃₉F₄N₅O₂ 602.30 602.4 64 tBu CN C₃₂H₄₀N₆O₂ 541.32 541.2 65 tBu OCHF₂ C₃₂H₄₁F₂N₅O₃ 582.32 582.4 66 tBu C₃₁H₄₁N₅O₂ 516.33 516.2 67 tBu CH₃ C₃₂H₄₃N₅O₂ 530.34 530.4 68 tBu CF₃ C₃₂H₄₀F₃N₅O₂ 584.31 584.4 69 tBu F C₃₁H₄₀FN₅O₂ 534.32 534.2 70 tBu CF₃ C₃₂H₄₀F₃N₅O₂ 584.31 584.4 71 tBu Cl C₃₁H₄₀ClN₅O₂ 550.29 550.2 72 tBu CF₃ C₃₂H₄₀F₃N₅O₂ 584.31 584.4 73 tBu CH₃ C₃₂H₄₃N₅O₂ 530.34 530.4 74 tBu Cl C₃₁H₄₀ClN₅O₂ 550.29 550.2 75 tBu OCH₃ C₃₂H₄₃N₅O₃ 546.34 546.4 76 tBu F F C₃₁H₃₉F₂N₅O₂ 552.31 552.4 77 tBu F F C₃₁H₃₉F₂N₅O₂ 552.31 552.2 78 tBu F F C₃₁H₃₉F₂N₅O₂ 552.31 552.2 79 tBu F F C₃₁H₃₉F₂N₅O₂ 552.31 552.4 80 tBu F F C₃₁H₃₉F₂N₅O₂ 552.31 552.4 81 tBu F F C₃₁H₃₉F₂N₅O₂ 552.31 552.2 82 tBu F Cl C₃₁H₃₉ClFN₅O₂ 568.28 568.2 83 tBu CF₃ CF₃ C₃₃H₃₉F₆N₅O₂ 652.30 652.2 84 iPr OCF₃ C₃₁H₃₈F₃N₅O₃ 586.29 586.2 85 iPr OCF₃ C₃₁H₃₈F₃N₅O₃ 586.29 586.2 86 tBu OCF₃ C₃₂H₄₀F₃N₅O₃ 600.31 600.2 87 tBu OCF₃ C₃₂H₄₀F₃N₅O₃ 600.31 600.2

TABLE III

Ex- am- [M + [M + ple Molecular H]⁺ H]⁺ No. R¹ R³ Formula calcd found 88 iPr N(CH₃)₂ C₂₆H₄₀N₆O₂ 469.32 469.4 89 iPr morpholin-1-yl C₂₈H₄₂N₆O₃ 511.33 511.4 90 iPr CH₃ C₂₅H₃₇N₅O₂ 440.30 440.2 91 iPr tetrahydrofuran-2-yl C₂₈H₄₁N₅O₃ 496.32 496.4 92 iPr —CH₂-thiophen-3-yl C₂₉H₃₉N₅O₂S 522.28 522.2 93 iPr 2,2-dimethylpropyl C₂₉H₄₅N₅O₂ 496.36 496.4 94 iPr —CH₂-thiophen-2-yl C₂₉H₃₉N₅O₂S 522.28 522.2 95 iPr cyclohexyl C₃₀H₄₅N₅O₂ 508.36 508.4 96 iPr (S)-1-methylpropyl C₂₈H₄₃N₅O₂ 482.34 482.4 97 iPr —CH₂-naphth-1-yl C₃₅H₄₃N₅O₂ 566.34 566.4 98 iPr cyclopentyl C₃₀H₄₅N₅O₂ 508.36 508.4 99 iPr (R)-tetrahydrofuran-2-yl C₂₈H₄₁N₅O₃ 496.32 496.4 100 tBu furan-2-yl C₂₉H₃₉N₅O₃ 506.31 506.2 101 tBu —CH₂-thiophen-3-yl C₃₀H₄₁N₅O₂S 536.30 536.2 102 tBu 2,2-dimethylpropyl C₃₀H₄₇N₅O₂ 510.37 510.4 103 tBu —CH₂-thiophen-2-yl C₃₀H₄₁N₅O₂S 536.30 536.2 104 tBu (S)-1-methylpropyl C₂₉H₄₅N₅O₂ 496.36 496.4 105 tBu —CH₂-naphth-1-yl C₃₆H₄₅N₅O₂ 580.36 580.4 106 tBu (R)-tetrahydrofuran-2-yl C₂₉H₄₃N₅O₃ 510.34 510.4 107 tBu (S)-4-oxo-azetidin-2-yl C₂₈H₄₀N₆O₃ 509.32 510.4 108 tBu pyridin-2-yl C₃₁H₄₂N₆O₂ 531.34 531.2

TABLE IV

Example Molecular [M + H]⁺ [M + H]⁺ No. R¹ R^(5a) R^(5b) R^(5c) R^(5d) R^(5e) Formula calcd found 109 iPr CH₃ C₃₁H₄₂N₆O₂ 531.34 531.4 110 iPr F C₃₀H₃₉FN₆O₂ 535.31 535.2 111 iPr CF₃ C₃₁H₃₉F₃N₆O₂ 585.31 585.2 112 iPr OCF₃ C₃₁H₃₉F₃N₆O₃ 601.30 601.2 113 iPr OCHF₂ C₃₁H₄₀F₂N₆O₃ 583.31 583.2 114 iPr C₃₀H₄₀N₆O₂ 517.32 517.4 115 iPr CH₃ CH₃ C₃₂H₄₄N₆O₂ 545.35 545.4 116 iPr OCF₃ C₃₁H₃₉F₃N₆O₃ 601.30 601.2 117 iPr tBu C₃₄H₄₈N₆O₂ 573.38 573.4 118 iPr Cl C₃₀H₃₉ClN₆O₂ 551.28 551.2 119 tBu Cl C₃₁H₄₁ClN₆O₂ 565.30 565.2 120 tBu CH₃ C₃₂H₄₄N₆O₂ 545.35 545.5 121 tBu F C₃₁H₄₁FN₆O₂ 549.33 549.2 122 tBu CF₃ C₃₂H₄₁F₃N₆O₂ 599.32 599.2 123 tBu OCF₃ C₃₂H₄₁F₃N₆O₃ 615.32 615.2 124 tBu OCHF₂ C₃₂H₄₂F₂N₆O₃ 597.33 597.4 125 tBu F C₃₁H₄₁FN₆O₂ 549.33 549.2 126 tBu C₃₁H₄₂N₆O₂ 531.34 531.4 127 tBu CH₃ CH₃ C₃₃H₄₆N₆O₂ 559.37 559.4 128 tBu OCF₃ C₃₂H₄₁F₃N₆O₃ 615.32 615.2 129 tBu tBu C₃₅H₅₀N₆O₂ 587.40 587.4

TABLE V

Example Molecular [M + H]⁺ [M + H]⁺ No. R¹ R⁶ R⁷ R^(8a) R^(8b) R^(8c) R^(8d) Formula calc found 130 iPr (S)—OH C₃₁H₄₁N₅O₃ 532.32 532.2 131 iPr oxo C₃₁H₃₉N₅O₃ 530.31 530.2 132 iPr Cl C₃₁H₄₀ClN₅O₂ 550.29 550.2 133 iPr (S)—CH₃ C₃₂H₄₃N₅O₂ 530.34 530.4 134 iPr —(CH₂)₂— C₃₃H₄₃N₅O₂ 542.34 542.4 135 iPr F F C₃₁H₃₉F₂N₅O₂ 552.31 552.2 136 iPr F C₃₁H₄₀FN₅O₂ 534.32 534.2 137 iPr Cl C₃₁H₄₀ClN₅O₂ 550.29 551.2 138 iPr F F C₃₁H₃₉F₂N₅O₂ 552.31 552.2 139 iPr F F C₃₁H₃₉F₂N₅O₂ 552.31 553.2 140 iPr C₃₁H₄₁N₅O₂ 516.33 516.4 141 tBu (S)—OH C₃₂H₄₃N₅O₃ 546.34 546.4 142 tBu F C₃₂H₄₂FN₅O₂ 548.33 548.2 143 tBu oxo C₃₂H₄₁N₅O₃ 544.32 544.4 144 tBu Cl C₃₂H₄₂ClN₅O₂ 564.30 565.2 145 tBu CH₃ 2-methylpropyl C₃₇H₅₃N₅O₂ 600.42 600.4 146 tBu (S)—CH₃ C₃₃H₄₅N₅O₂ 544.36 544.4 147 tBu —(CH₂)₂— C₃₄H₄₅N₅O₂ 556.36 556.4 148 tBu Cl Cl C₃₂H₄₁Cl₂N₅O₂ 598.26 599.2 149 tBu F F C₃₂H₄₁F₂N₅O₂ 566.32 566.2 150 tBu F C₃₂H₄₂FN₅O₂ 548.33 548.4 151 tBu CF₃ C₃₃H₄₂F₃N₅O₂ 598.33 598.4 152 tBu CF₃ C₃₃H₄₂F₃N₅O₂ 598.33 598.2 153 tBu Cl C₃₂H₄₂ClN₅O₂ 564.30 564.2 154 tBu F F C₃₂H₄₁F₂N₅O₂ 566.32 566.2 155 tBu F F C₃₂H₄₁F₂N₅O₂ 566.32 566.4 156 tBu C₃₂H₄₃N₅O₂ 530.34 530.4

TABLE VI

Example [M + H]⁺ [M + H]⁺ No. R¹ R⁷ R^(8a) Molecular Formula calcd found 157 iPr (R)—OH C₃₁H₄₇N₅O₃ 538.37 538.4 158 iPr C₃₁H₄₇N₅O₂ 522.37 522.4 159 tBu (R)—OH C₃₂H₄₉N₅O₃ 552.38 552.4 160 tBu C₃₂H₄₉N₅O₂ 536.39 536.4

TABLE VII

Example Molecular [M + H]⁺ [M + H]⁺ No. R¹ R⁹ R^(10a) R^(10b) Formula calcd found 161 iPr CH₃ C₃₂H₄₃N₅O₃ 546.34 546.4 162 iPr Cl Cl C₃₁H₃₉Cl₂N₅O₃ 600.24 601.2 163 iPr CH₃ Cl C₃₂H₄₂ClN₅O₃ 580.30 581.2 164 iPr CH₃ C₃₂H₄₃N₅O₃ 546.34 546.4 165 tBu CH₃ C₃₃H₄₅N₅O₃ 560.35 560.4 166 tBu Cl Cl C₃₂H₄₁Cl₂N₅O₃ 614.26 615.2 167 tBu CH₃ Cl C₃₃H₄₄ClN₅O₃ 594.31 595.2 168 tBu CH₃ C₃₃H₄₅N₅O₃ 560.35 560.4

TABLE VIII

Ex- am- [M + [M + ple Molecular H]⁺ H]⁺ No. R¹ R¹¹ Formula calcd found 169 iPr CH₃ C₂₄H₃₇N₅O₃S 476.26 476.2 170 iPr 2,4-dimethylisoxazol-2yl C₂₈H₄₀N₆O₄S 557.28 557.2 171 iPr —CH₂-phenyl C₃₀H₄₁N₅O₃S 552.29 552.2 172 tBu 2,4-dimethylisoxazol-2yl C₂₉H₄₂N₆O₄S 571.30 571.2 173 tBu —CH₂-phenyl C₃₁H₄₃N₅O₃S 566.31 566.2

TABLE IX

Example Molecular [M + H]⁺ [M + H]⁺ No. R¹ R^(11a) R^(11b) R^(11c) R^(11d) Formula calcd found 174 iPr CF₃ C₃₀H₃₈F₃N₅O₃S 606.27 606.2 175 iPr CN C₃₀H₃₈N₆O₃S 563.27 563.2 176 iPr OCH₃ C₃₀H₄₁N₅O₄S 568.29 568.2 177 iPr Cl C₂₉H₃₈ClN₅O₃S 572.24 572.2 178 iPr F C₂₉H₃₈FN₅O₃S 556.27 556.2 179 iPr CF₃ C₃₀H₃₈F₃N₅O₃S 606.27 606.2 180 iPr iPr C₃₂H₄₅N₅O₃S 580.32 580.4 181 iPr Cl C₂₉H₃₈ClN₅O₃S 572.24 572.2 182 iPr CH₃ F C₃₀H₄₆FN₅O₃S 570.28 570.2 183 iPr Cl F C₂₉H₃₇ClFN₅O₃S 590.23 590.2 184 iPr CH₃ Cl C₃₀H₄₀ClN₅O₃S 586.25 586.2 185 iPr tBu C₃₃H₄₇N₅O₃S 594.34 594.4 186 iPr OCH₃ Cl C₃₀H₄₀ClN₅O₄S 602.25 602.2 187 iPr Cl C₂₉H₃₈ClN₅O₃S 572.24 572.2 188 iPr C₂₉H₃₉N₅O₃S 538.28 538.2 189 iPr F C₂₉H₃₈FN₅O₃S 556.27 556.2 190 iPr CH₃ C₃₀H₄₁N₅O₃S 552.29 552.2 191 iPr CH₃ C₃₀H₄₁N₅O₃S 552.29 552.2 192 iPr CF₃ C₃₀H₃₈F₃N₅O₃S 606.27 606.2 193 iPr CH₃ C₃₀H₄₁N₅O₃S 552.29 552.2 194 tBu CN C₃₁H₄₀N₆O₃S 577.29 577.2 195 tBu CF₃ C₃₁H₄₀F₃N₅O₃S 620.28 620.2 196 tBu iPr C₃₃H₄₇N₅O₃S 594.34 594.4 197 tBu Cl C₃₀H₄₀ClN₅O₃S 586.25 586.2 198 tBu CH₃ F C₃₁H₄₂FN₅O₃S 584.30 584.2 199 tBu Cl F C₃₀H₃₉ClFN₅O₃S 604.24 604.2 200 tBu CH₃ Cl C₃₁H₄₂ClN₅O₃S 600.27 600.2 201 tBu tBu C₃₄H₄₉N₅O₃S 608.36 608.4 202 tBu OCH₃ Cl C₃₁H₄₂ClN₅O₄S 616.26 616.2 203 tBu CH₃ C₃₁H₄₃N₅O₃S 566.31 566.4 204 tBu CH₃ C₃₁H₄₃N₅O₃S 566.31 566.2 205 tBu CF₃ C₃₁H₄₀F₃N₅O₃S 620.28 620.2 206 tBu CH₃ C₃₁H₄₃N₅O₃S 566.31 566.2 207 tBu CF₃ C₃₁H₄₀F₃N₅O₃S 620.28 620.2 208 tBu OCH₃ C₃₁H₄₃N₅O₄S 582.30 582.2 209 tBu Cl C₃₀H₄₀ClN₅O₃S 586.25 586.2 210 tBu F C₃₀H₄₀FN₅O₃S 570.28 570.2 211 tBu Cl C₃₀H₄₀ClN₅O₃S 586.25 586.2 212 tBu C₃₀H₄₁N₅O₃S 552.29 552.2 213 tBu F C₃₀H₄₀FN₅O₃S 570.28 570.2

Example 214 Alternate synthesis of 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester a. Preparation of 4-hydroxymethyl-piperidine-1-carboxylic acid methyl ester

4-Hydroxymethylpiperidine (1.0 g, 8.6 mmol) was dissolved in water (15 mL) and cooled to 0° C. To this solution was added dropwise a solution of potassium carbonate (4.8 g, 34.7 mmol) in water (10 mL), followed by methyl chloroformate (2.68 mL, 34.7 mmol). The mixture was stirred vigorously and allowed to warm to room temperature over 2 h. After stirring overnight (16 h), the reaction mixture was acidified with 6M aqueous hydrochloric acid and extracted with dichloromethane (3×60 mL). The extracts were combined, dried over sodium sulfate and filtered. The filtrate was evaporated to yield the title intermediate (1.4 g, 8.1 mmol, 93%) as a colorless oil. (m/z): C₈H₁₅NO₃ calcd. 173.11. found 156.2 [M−H₂O+H]⁺. ¹H NMR (300 MHz, DMSO-d₆): δ (ppm) 0.98 (m, 2H), 1.52 (m, 1H), 1.63 (br d, 2H), 2.72 (br m, 2H), 3.23 (d, 2H), 3.56 (s; 3H), 3.95 (br d, 2H), 4.48 (br s, 1H).

b. Preparation of 4-formylpiperidine-1-carboxylic acid methyl ester

To a solution of oxalyl chloride (4.1 mL, 8.2 mmol) in dichloromethane (4 mL) at −78° C. was added dropwise a solution of dimethylsulfoxide (1.2 mL, 16.4 mmol) in dichloromethane (4 mL). After stirring for 5 min, a solution of 4-hydroxymethyl-piperidine-1-carboxylic acid methyl ester (1.3 g, 7.5 mmol) in dichloromethane (5 mL) was added. The resulting solution was stirred for another 5 min, then triethylamine (5.2 mL, 37.3 mmol) was added and the mixture allowed to warm to −10° C. After stirring for 1 h, dichloromethane (100 mL) was added, and the organic layer was washed with 1M aqueous phosphoric acid, 1M aqueous sodium hydroxide, and brine. The solution was dried over sodium sulfate then evaporated to afford the title intermediate as a wheat colored oil (1.0 g, 5.8 mmol, 78%). ¹H NMR (300 MHz, DMSO-d₆): δ (ppm) 1.36 (m, 2H), 1.83 (m, 2H), 2.48 (br m, 1H), 2.93 (br t, 2H), 3.56 (s, 3H), 3.80 (br d, 2H), 9.56 (s, 1H).

c. Synthesis of 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester

2-Isopropyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide, (bis TFA salt; 1.1 g, 2.0 mmol) was suspended in dichloromethane (20 mL) and N,N-di-isopropylethylamine (0.72 mL, 4.0 mmol) was added. When the suspension became a clear solution, acetic acid (0.13 mL, 2.0 mmol) was added, followed by a solution of 4-formylpiperidine-1-carboxylic acid methyl ester (0.54 g, 3.1 mmol) in dichloromethane (20 mL). After stirring for 5 minutes at room temperature, sodium triacetoxyborohydride (0.628 g, 3.1 mmol) was added, and the reaction stirred for an additional 1 h. The aqueous layer was then made alkaline with 1M aqueous sodium hydroxide (35 mL) and extracted with dichloromethane (2×20 mL). The combined organic layers were washed with brine, dried over sodium sulfate and evaporated to yield crude product as a brown solid (1.41 g).

The crude product was purified via preparative HPLC (reverse phase) [gradient of 5-10-25%: 5% MeCN/water (0.1% TFA) to 10% MeCN linear over 10 min; 10% MeCN to 25% MeCN linear over 50 min; flow rate=15 mL/min; detection at 280 nm] to provide the title compound as the bis trifluoroacetate salt, which was then lyophilized. A mixture of 1M sodium hydroxide and dichloromethane (1:1, 100 mL) was added to the lyophilized bis trifluoroacetate salt. The organic layer was dried over sodium sulfate, filtered, and evaporated, and the resulting solid was lyophilized to provide the title compound as a white solid (0.93 g, 2 mmol, 98% yield, purity 97.5%). (m/z): [M+H]⁺ calcd for C₂₅H₃₇N₅O₃ 456.30. found 456.3. Retention time (anal. HPLC: 2-50% MeCN/H₂O over 6 min)=3.06 min. ¹H NMR (300 MHz, DMSO-d₆): 0.92 (m, 2H), 1.30 (m, 2H), 1.38 (d, 6H), 1.53 (m, 1H), 1.60-1.90 (m, 7H), 2.07 (d, 2H), 2.73 (br m, 2H), 2.83 (br d, 2H), 3.22 (septet, 1H), 3.33 (t, 2H), 3.56 (s, 3H), 3.93 (br d, 2H), 7.23 (t, 1H), 7.62 (d, 1H), 7.77 (d, 1H), 10.10 (br s, 1H).

Example 215 Synthesis of crystalline 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester

4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester in amorphous solid form, prepared according to the process of Example 214 (300 mg) was dissolved in acetonitrile (15 mL), mixed until complete dissolution, and exposed to the atmosphere resulting in partial evaporation. Crystals were observed to have nucleated within 2 h. Chemical composition of the crystals was confirmed by ¹H NMR, liquid chromatography/mass spectrometry (LC/MS), and x-ray structure analysis. Crystalline nature of the solid product was confirmed by powder x-ray diffraction, differential scanning calorimetry, and x-ray structure analysis.

Example 216 Synthesis of crystalline 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester a. Preparation of 4-hydroxymethyl-piperidine-1-carboxylic acid methyl ester

4-Hydroxymethylpiperidine (47.6 g, 1.0 eq) and water (300 mL) were charged to a flask. The resulting mixture was cooled to 0-10° C. Potassium carbonate (85.7 g, 1.5 eq) dissolved in water (150 mL) and methyl chloroformate (38.4 mL, 1.1 eq) were added while maintaining the temperature at below 10° C. When the addition was complete, the reaction mixture was warmed up to 20-30° C. for 1 hour. After the reaction was complete, dichloromethane (500 mL) was added to the reaction mixture. The organic layer was collected and washed with 1 M phosphoric acid solution (200 mL), saturated sodium bicarbonate solution (200 mL) and saturated sodium chloride solution (200 mL). The organic layer was dried over sodium sulfate (50 g, 1 w/w eq) and then distilled under vacuum to produce the title intermediate. (67.0 g, 90% yield)

b. Preparation of 4-formylpiperidine-1-carboxylic acid methyl ester

4-Hydroxymethylpiperidine-1-carboxylic acid methyl ester (34.7 g, 1.0 eq) was dissolved in dichloromethane and cooled to 0-10° C. A solution of sodium bicarbonate (2.35 g, 0.14 eq) and sodium bromide (2.40 g, 0.10 eq) in water (100 mL) was added over 15 min while maintaining the temperature at 0-10° C. 2,2,6,6-Tetramethyl-1-piperidinyloxy free radical (TEMPO) (0.32 g, 0.01 eq) was added to the mixture, followed by 10-13% w/v sodium hypochlorite solution (135 mL, 1.1 eq) over 1 h with good agitation while maintaining the temperature at 0-10° C. After the reaction was complete, the layers were separated and the organic layer washed with water (150 mL) and dried over sodium sulfate (30 g, 1 w/w eq). The solvent was removed by distillation to provide the title intermediate. (31.0 g, 90% yield)

c. Preparation of 2-isopropyl-1H-benzoimidazole-4-carboxylic acid (piperidin-4-ylmethyl)amide

Trifluoroacetic acid (56.0 mL, 10 eq) was added to a flask containing a ˜5° C. solution of 4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)amino]methyl}-piperidine-1-carboxylic acid tert-butyl ester (30.0 g, 1.0 eq) in dichloromethane (300 mL) while maintaining the temperature below 10° C. The resulting mixture was stirred at 20-30° C. for 2 h. When the reaction was complete, triethylamine (73.2 mL, 7.0 eq) and acetic acid (4.3 mL, 1.0 eq) were added to provide a solution of the title intermediate with an apparent pH of approximately 4 that was used directly in the next step.

d. Synthesis of 4-(4-{[(2-isopropyl-1H-benzoimidazole-4-carbonyl)-amino]methyl}piperidin-1-ylmethyl)piperidine-1-carboxylic acid methyl ester

4-Formylpiperidine-1-carboxylic acid methyl ester (25.7 g, 2.0 eq) was added to the solution prepared in the previous step while maintaining the temperature at 20-30° C. After stirring for 30 min, sodium triacetoxyborohydride (24.3 g, 1.5 eq) was added while maintaining the temperature at 20-30° C. The reaction mixture was stirred at 20-30° C. for 30 min. After the reaction was complete, 1 M hydrochloric acid (300 mL) was added to quench the reaction. The product-containing aqueous layer was collected and washed with dichloromethane (150 mL). The aqueous layer was treated with activated carbon (Darco G60, 6 g, 20% w/w) to remove color. The suspension was stirred for 1 hr, and then filtered through a bed of Celite. Dichloromethane (300 mL) was added to the aqueous solution and the product free-based using 4 N sodium hydroxide by adjusting the pH of the aqueous layer to 12-13. The organic layer was collected and washed with water (300 mL). The organic layer was distilled at 80° C. and solvent exchanged with acetonitrile (2×300 mL), to remove dichloromethane and residual triethylamine. The solids were suspended in acetonitrile (600 mL), and the mixture heated until the solids were dissolved (˜75° C.). The solution was cooled until nucleation occurred (˜55-65° C.) and held for 1 h. The slurry was cooled to 20° C. over 2 h, and then to 0-5° C. over 30 min, followed by stirring at 0-5° C. for 30 min. The solids were filtered and washed with cold acetonitrile (60 mL). The wet cake was dried under vacuum at 60° C. for 6 h to provide the title compound. (28.3 g, 85% yield).

Assay 1: Radioligand Binding Assay on 5-HT_(4(c)) Human Receptors

a. Membrane Preparation 5-HT_(4(c))

HEK-293 (human embryonic kidney) cells stably-transfected with human 5-HT_(4(c)) receptor cDNA (Bmax=˜6.0 pmol/mg protein, as determined using [³H]-GR113808 membrane radioligand binding assay) were grown in T-225 flasks in Dulbecco's Modified Eagles Medium (DMEM) containing 4,500 mg/L D-glucose and pyridoxine hydrochloride (GIBCO-Invitrogen Corp., Carlsbad Calif.: Cat #11965) supplemented with 10% fetal bovine serum (FBS) (GIBCO-Invitrogen Corp.: Cat #10437), 2 mM L-glutamine and (100 units) penicillin-(100 μg) streptomycin/ml (GIBCO-Invitrogen Corp.: Cat #15140) in a 5% CO₂, humidified incubator at 37° C. Cells were grown under continuous selection pressure by the addition of 800 μg/mL geneticin (GIBCO-Invitrogen Corp.: Cat #10131) to the medium.

Cells were grown to roughly 60-80% confluency (<35 subculture passages). At 20-22 hours prior to harvesting, cells were washed twice and fed with serum-free DMEM. All steps of the membrane preparation were performed on ice. The cell monolayer was lifted by gentle mechanical agitation and trituration with a 25 mL pipette. Cells were collected by centrifugation at 1000 rpm (5 min).

For the membrane preparation, cell pellets were resuspended in ice-cold 50 mM 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES), pH 7.4 (membrane preparation buffer) (40 mL/total cell yield from 30-40 T225 flasks) and homogenized using a polytron disrupter (setting 19, 2×10 s) on ice. The resultant homogenates were centrifuged at 1200 g for 5 min at 4° C. The pellet was discarded and the supernatant centrifuged at 40,000 g (20 min). The pellet was washed once by resuspension with membrane preparation buffer and centrifugation at 40,000 g (20 min). The final pellet was resuspended in 50 mM HEPES, pH 7.4 (assay buffer) (equivalent 1 T225 flask/1 mL). Protein concentration of the membrane suspension was determined by the method of Bradford (Bradford, 1976). Membranes were stored frozen in aliquots at −80° C.

b. Radioligand Binding Assays

Radioligand binding assays were performed in 1.1 mL 96-deep well polypropylene assay plates (Axygen) in a total assay volume of 400 μL containing 2 μg membrane protein in 50 mM HEPES pH 7.4, containing 0.025% bovine serum albumin (BSA). Saturation binding studies for determination of K_(d) values of the radioligand were performed using [³H]-GR113808 (Amersham Inc., Bucks, UK: Cat #TRK944; specific activity ˜82 Ci/mmol) at 8-12 different concentrations ranging from 0.001 nM-5.0 nM. Displacement assays for determination of pK_(i) values of compounds were performed with [³H]-GR113808 at 0.15 nM and eleven different concentrations of compound ranging from 10 μM-100 μM.

Test compounds were received as 10 mM stock solutions in DMSO and diluted to 400 μM into 50 mM HEPES pH 7.4 at 25° C., containing 0.1% BSA, and serial dilutions (1:5) then made in the same buffer. Non-specific binding was determined in the presence of 1 μM unlabeled GR113808. Assays were incubated for 60 min at room temperature, and then the binding reactions were terminated by rapid filtration over 96-well GF/B glass fiber filter plates (Packard BioScience Co., Meriden, Conn.) presoaked in 0.3% polyethyleneimine. Filter plates were washed three times with filtration buffer (ice-cold 50 mM HEPES, pH7.4) to remove unbound radioactivity. Plates were dried, 35 μL Microscint-20 liquid scintillation fluid (Packard BioScience Co., Meriden, Conn.) was added to each well and plates were counted in a Packard Topcount liquid scintillation counter (Packard BioScience Co., Meriden, Conn.).

Binding data were analyzed by nonlinear regression analysis with the GraphPad Prism Software package (GraphPad Software, Inc., San Diego, Calif.) using the 3-parameter model for one-site competition. The BOTTOM (curve minimum) was fixed to the value for nonspecific binding, as determined in the presence of 1 μM GR113808. K_(i) values for test compounds were calculated, in Prism, from the best-fit IC₅₀ values, and the IQ value of the radioligand, using the Cheng-Prusoff equation (Cheng and Prusoff, Biochemical Pharmacology, 1973, 22, 3099-108): K_(i)=IC₅₀/(1+[L]/K_(d)) where [L]=concentration [³H]-GR113808. Results are expressed as the negative decadic logarithm of the K_(i) values, pK_(i).

Test compounds having a higher pK_(i) value in this assay have a higher binding affinity for the 5-HT₄ receptor. The compounds of the invention which were tested in this assay had a pK_(i) value ranging from about 7.0 to about 10.0.

Assay 2: Radioligand Binding Assay on 5-HT_(3A) Human Receptors: Determination of Receptor Subtype Selectivity

a. Membrane Preparation 5-HT_(3A)

HEK-293 (human embryonic kidney) cells stably-transfected with human 5-HT_(3A) receptor cDNA were obtained from Dr. Michael Bruess (University of Bonn, GDR) (Bmax=˜9.0 pmol/mg protein, as determined using [³H]-GR65630 membrane radioligand binding assay). Cells were grown in T-225 flasks or cell factories in 50% Dulbecco's Modified Eagles Medium (DMEM) (GIBCO-Invitrogen Corp., Carlsbad, Calif.: Cat #11965) and 50% Ham's F12 (GIBCO-Invitrogen Corp.: Cat #11765) supplemented with 10% heat inactivated fetal bovine serum (FBS) (Hyclone, Logan, Utah: Cat #SH30070.03) and (50 units) penicillin-(50 μg) streptomycin/ml (GIBCO-Invitrogen Corp.: Cat #15140) in a 5% CO₂, humidified incubator at 37° C.

Cells were grown to roughly 70-80% confluency (<35 subculture passages). All steps of the membrane preparation were performed on ice. To harvest the cells, the media was aspirated and cells were rinsed with Ca²⁺, Mg²⁺-free Dulbecco's phosphate buffered saline (dPBS). The cell monolayer was lifted by gentle mechanical agitation. Cells were collected by centrifugation at 1000 rpm (5 min). Subsequent steps of the membrane preparation followed the protocol described above for the membranes expressing 5-HT_(4(c)) receptors.

b. Radioligand Binding Assays

Radioligand binding assays were performed in 96-well polypropylene assay plates in a total assay volume of 200 μL containing 1.5-2 μg membrane protein in 50 mM HEPES pH 7.4, containing 0.025% BSA assay buffer. Saturation binding studies for determination of K_(d) values of the radioligand were performed using [³H]-GR65630 (PerkinElmer Life Sciences Inc., Boston, Mass.: Cat #NET1011, specific activity ˜85 Ci/mmol) at twelve different concentrations ranging from 0.005 nM to 20 nM. Displacement assays for determination of pK_(i) values of compounds were performed with [³H]-GR65630 at 0.50 nM and eleven different concentrations of compound ranging from 10 pM to 100 μM. Compounds were received as 10 mM stock solutions in DMSO (see section 3.1), diluted to 400 μM into 50 mM HEPES pH 7.4 at 25° C., containing 0.1% BSA, and serial (1:5) dilutions then made in the same buffer. Non-specific binding was determined in the presence of 10 μM unlabeled MDL72222. Assays were incubated for 60 min at room temperature, then the binding reactions were terminated by rapid filtration over 96-well GF/B glass fiber filter plates (Packard BioScience Co., Meriden, Conn.) presoaked in 0.3% polyethyleneimine. Filter plates were washed three times with filtration buffer (ice-cold 50 mM HEPES, pH7.4) to remove unbound radioactivity. Plates were dried, 35 μL Microscint-20 liquid scintillation fluid (Packard BioScience Co., Meriden, Conn.) was added to each well and plates were counted in a Packard Topcount liquid scintillation counter (Packard BioScience Co., Meriden, Conn.).

Binding data were analyzed using the non-linear regression procedure described above to determine K_(i) values. The BOTTOM (curve minimum) was fixed to the value for nonspecific binding, as determined in the presence of 10 μM MDL72222. The quantity [L] in the Cheng-Prusoff equation was defined as the concentration [³H]-GR65630.

Selectivity for the 5-HT₄ receptor subtype with respect to the 5-HT₃ receptor subtype was calculated as the ratio K_(i)(5-HT_(3A))/K_(i)(5-HT_(4(c)). The compounds of the invention which were tested in this assay had a 5-HT₄/5-HT₃ receptor subtype selectivity ranging from about 4000 to upwards of 400,000.

Assay 3: Whole-Cell cAMP Accumulation Flashplate Assay with HEK-293 Cells Expressing Human 5-HT_(4(c)) Receptors

In this assay, the functional potency of a test compound was determined by measuring the amount of cyclic AMP produced when HEK-293 cells expressing 5-HT₄ receptors were contacted with different concentrations of test compound.

a. Cell Culture

HEK-293 (human embryonic kidney) cells stably-transfected with cloned human 5-HT_(4(c)) receptor cDNA were prepared expressing the receptor at two different densities: (1) at a density of about 0.5-0.6 pmol/mg protein, as determined using a [³H]-GR113808 membrane radioligand binding assay, and (2) at a density of about 6.0 pmol/mg protein. The cells were grown in T-225 flasks in Dulbecco's Modified Eagles Medium (DMEM) containing 4,500 mg/L D-glucose (GIBCO-Invitrogen Corp.: Cat #11965) supplemented with 10% fetal bovine serum (FBS) (GIBCO-Invitrogen Corp.: Cat #10437) and (100 units) penicillin-(100 μg) streptomycin/ml (GIBCO-Invitrogen Corp.: Cat #15140) in a 5% CO₂, humidified incubator at 37° C. Cells were grown under continuous selection pressure by the addition of geneticin (800 μg/mL: GIBCO-Invitrogen Corp.: Cat #10131) to the medium.

b. Cell Preparation

Cells were grown to roughly 60-80% confluency. Twenty to twenty-two hours prior to assay, cells were washed twice, and fed, with serum-free DMEM containing 4,500 mg/L D-glucose (GIBCO-Invitrogen Corp.: Cat #11965). To harvest the cells, the media was aspirated and 10 mL Versene (GIBCO-Invitrogen Corp.: Cat #15040) was added to each T-225 flask. Cells were incubated for 5 min at RT and then dislodged from the flask by mechanical agitation. The cell suspension was transferred to a centrifuge tube containing an equal volume of pre-warmed (37° C.) dPBS and centrifuged for 5 min at 1000 rpm. The supernatant was discarded and the pellet was re-suspended in pre-warmed (37° C.) stimulation buffer (10 mL equivalent per 2-3 T-225 flasks). This time was noted and marked as time zero. The cells were counted with a Coulter counter (count above 8 μm, flask yield was 1−2×10⁷ cells/flask). Cells were resuspended at a concentration of 5×10⁵ cells/ml in pre-warmed (37° C.) stimulation buffer (as provided in the flashplate kit) and preincubated at 37° C. for 10 min.

cAMP assays were performed in a radioimmunoassay format using the Flashplate Adenylyl Cyclase Activation Assay System with ¹²⁵I-cAMP (SMP004B, PerkinElmer Life Sciences Inc., Boston, Mass.), according to the manufacturer's instructions.

Cells were grown and prepared as described above. Final cell concentrations in the assay were 25×10³ cells/well and the final assay volume was 100 μL. Test compounds were received as 10 mM stock solutions in DMSO, diluted to 400 μM into 50 mM HEPES pH 7.4 at 25° C., containing 0.1% BSA, and serial (1:5) dilutions then made in the same buffer. Cyclic AMP accumulation assays were performed with 11 different concentrations of compound ranging from 10 pM to 100 μM (final assay concentrations). A 5-HT concentration-response curve (10 pM to 100 μM) was included on every plate. The cells were incubated, with shaking, at 37° C. for 15 min and the reaction terminated by addition of 100 μl of ice-cold detection buffer (as provided in the flashplate kit) to each well. The plates were sealed and incubated at 4° C. overnight. Bound radioactivity was quantified by scintillation proximity spectroscopy using the Topcount (Packard BioScience Co., Meriden, Conn.).

The amount of cAMP produced per mL of reaction was extrapolated from the cAMP standard curve, according to the instructions provided in the manufacturer's user manual. Data were analyzed by nonlinear regression analysis with the GraphPad Prism Software package using the 3-parameter sigmoidal dose-response model (slope constrained to unity). Potency data are reported as pEC₅₀ values, the negative decadic logarithm of the EC₅₀ value, where EC₅₀ is the effective concentration for a 50% maximal response.

Test compounds exhibiting a higher pEC₅₀ value in this assay have a higher potency for agonizing the 5-HT₄ receptor. The compounds of the invention which were tested in this assay, for example, in the cell line (1) having a density of about 0.5-0.6 pmol/mg protein, had a pEC₅₀ value ranging from about 7.5 to about 9.5.

Assay 4: In Vitro Voltage Clamp Assay of Inhibition of Potassium Ion Current in Whole Cells Expressing the hERG Cardiac Potassium Channel

CHO-K1 cells stably transfected with hERG cDNA were obtained from Gail Robertson at the University of Wisconsin. Cells were held in cryogenic storage until needed. Cells were expanded and passaged in Dulbecco's Modified Eagles Medium/F12 supplemented with 10% fetal bovine serum and 200 μg/mL geneticin. Cells were seeded onto poly-D-lysine (100 μg/mL) coated glass coverslips, in 35 mm² dishes (containing 2 mL medium) at a density that enabled isolated cells to be selected for whole cell voltage-clamp studies. The dishes were maintained in a humidified, 5% CO₂ environment at 37° C.

Extracellular solution was prepared at least every 7 days and stored at 4° C. when not in use. The extracellular solution contained (mM): NaCl (137), KCl (4), CaCl₂ (1.8), MgCl₂ (1), Glucose (10), 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) (10), pH 7.4 with NaOH. The extracellular solution, in the absence or presence of test compound, was contained in reservoirs, from which it flowed into the recording chamber at approximately 0.5 mL/min. The intracellular solution was prepared, aliquoted and stored at −20° C. until the day of use. The intracellular solution contained (mM): KCl (130), MgCl₂ (1), ethylene glycol-bis(beta-aminoethyl ether) N,N,N′,N′-tetra acetic acid salt (EGTA) (5), MgATP (5), 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) (10), pH 7.2 with KOH. All experiments were performed at room temperature (20-22° C.).

The coverslips on which the cells were seeded were transferred to a recording chamber and perfused continuously. Gigaohm seals were formed between the cell and the patch electrode. Once a stable patch was achieved, recording commenced in the voltage clamp mode, with the initial holding potential at −80 mV. After a stable whole-cell current was achieved, the cells were exposed to test compound. The standard voltage protocol was: step from the holding potential of −80 mV to +20 mV for 4.8 sec, repolarize to −50 mV for 5 sec and then return to the original holding potential (−80 mV). This voltage protocol was run once every 15 sec (0.067 Hz). Peak current amplitudes during the repolarization phase were determined using pClamp software. Test compounds at a concentration of 3 μM were perfused over the cells for 5 minutes, followed by a 5-minute washout period in the absence of compound. Finally a positive control (cisapride, 20 nM) was added to the perfusate to test the function of the cell. The step from −80 mV to +20 mV activates the hERG channel, resulting in an outward current. The step back to −50 mV results in an outward tail current, as the channel recovers from inactivation and deactivates.

Peak current amplitudes during the repolarization phase were determined using pCLAMP software. The control and test article data were exported to Origin® (OriginLab Corp., Northampton Mass.) where the individual current amplitudes were normalized to the initial current amplitude in the absence of compound. The normalized current means and standard errors for each condition were calculated and plotted versus the time course of the experiment.

Comparisons were made between the observed K⁺ current inhibitions after the five-minute exposure to either the test article or vehicle control (usually 0.3% DMSO). Statistical comparisons between experimental groups were performed using a two-population, independent t-test (Microcal Origin v. 6.0). Differences were considered significant at p<0.05.

The smaller the percentage inhibition of the potassium ion current in this assay, the smaller the potential for test compounds to change the pattern of cardiac repolarization when used as therapeutic agents. For example, the compounds of Examples 1-14 which were tested in this assay at a concentration of 3 μM exhibited an inhibition of the potassium ion current of less than about 30%, including, less than about 20%.

Assay 5: In Vitro Model of Oral Bioavailability: Caco-2 Permeation Assay

The Caco-2 permeation assay was performed to model the ability of test compounds to pass through the intestine and get into the blood stream after oral administration. The rate at which test compounds in solution permeate a cell monolayer designed to mimic the tight junction of human small intestinal monolayers was determined.

Caco-2 (colon, adenocarcinoma; human) cells were obtained from ATCC (American Type Culture Collection; Rockville, Md.). For the permeation study, cells were seeded at a density of 63,000 cells/cm² on pre-wetted transwells polycarbonate filters (Costar; Cambridge, Mass.). A cell monolayer was formed after 21 days in culture. Following cell culture in the transwell plate, the membrane containing the cell monolayer was detached from the transwell plate and inserted into the diffusion chamber (Costar; Cambridge, Mass.). The diffusion chamber was inserted into the heating block which was equipped with circulating external, thermostatically regulated 37° C. water for temperature control. The air manifold delivered 95% O₂/5% CO₂ to each half of a diffusion chamber and created a laminar flow pattern across the cell monolayer, which was effective in reducing the unstirred boundary layer.

The permeation study was performed with test compound concentrations at 100 μM and with ¹⁴C-mannitol to monitor the integrity of the monolayer. All experiments were conducted at 37° C. for 60 min. Samples were taken at 0, 30 and 60 min from both the donor and receiver sides of the chamber. Samples were analyzed by HPLC or liquid scintillation counting for test compound and mannitol concentrations. The permeation coefficient (K_(r)) in cm/sec was calculated.

In this assay, a K_(p) value greater than about 10×10⁻⁶ cm/sec is considered indicative of favorable bioavailability. Those compounds of the invention which were tested in this assay typically exhibited K_(p) values of between about 10×10⁻⁶ cm/sec and about 50×10⁻⁶ cm/sec.

Assay 6: Pharmacokinetic Study in the Rat

Aqueous solution formulations of test compounds were prepared in 0.1% lactic acid at a pH of between about 5 and about 6. Male Sprague-Dawley rats (CD strain, Charles River Laboratories, Wilmington, Mass.) were dosed with test compounds via intravenous administration (IV) at a dose of 2.5 mg/kg or by oral gavage (PO) at a dose of 5 mg/kg. The dosing volume was 1 mL/kg for IV and 2 mL/kg for PO administration. Serial blood samples were collected from animals pre-dose, and at 2 (IV only), 5, 15, and 30 min, and at 1, 2, 4, 8, and 24 hours post-dose. Concentrations of test compounds in blood plasma were determined by liquid chromatography-mass spectrometry analysis (LC-MS/MS) (MDS SCIEX, API 4000, Applied Biosystems, Foster City, Calif.) with a lower limit of quantitation of 1 ng/mL.

Standard pharmacokinetic parameters were assessed by non-compartmental analysis (Model 201 for IV and Model 200 for PO) using WinNonlin (Version 4.0.1, Pharsight, Mountain View, Calif.). The maximum in the curve of test compound concentration in blood plasma vs. time is denoted C_(max). The area under the concentration vs. time curve from the time of dosing to the last measurable concentration (AUC(0-t)) was calculated by the linear trapezoidal rule. Oral bioavailability (F(%)), i.e. the dose-normalized ratio of AUC(0-t) for PO administration to AUC(0-t) for IV administration, was calculated as:

F(%)=AUC _(PO) /AUC _(IV)×Dose_(IV)/Dose_(PO)×100%

Test compounds which exhibit larger values of the parameters C_(max), AUC(0-t), and F(%) in this assay are expected to have greater bioavailability when administered orally. Preferred compounds of the invention had C_(max) values typically ranging from about 0.06 to about 0.8 μg/mL and AUC(O-t) values typically ranging from about 0.14 to about 1.2 μg·hr/mL. By way of example, the compound of Example 1 had a C_(max) value of 0.8 μg/mL, an AUC(O-t) value of 1.2 μg·hr/mL and oral bioavailability (F(%)) in the rat model of about 75%.

While the present invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto. Additionally, all publications, patents, and patent documents cited hereinabove are incorporated by reference herein in full, as though individually incorporated by reference. 

1-22. (canceled)
 23. A method of studying a biological system or sample comprising a 5-HT₄ receptor, the method comprising: (a) contacting the biological system or sample with a compound of formula (I):

R¹ is C₃₋₄alkyl; and X is selected from: (a) —C(O)OR² wherein R² is C₁₋₃alkyl or phenyl; (b) —C(O)R³ wherein R³ is phenyl, optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl, halo, and —CF₃; furanyl; or thiophenyl; (c) —C(O)NR⁴R⁵ wherein R⁴ is hydrogen and R⁵ is phenyl optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo; (d) —C(O)C(R⁶R⁷)R⁸ wherein R⁶ is hydrogen and R⁷ is hydrogen, —OH, or methyl; or R⁶ and R⁷ taken together form oxo or —(CH₂)₂—; and R⁸ is phenyl or cyclohexyl, wherein phenyl or cyclohexyl are optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo; (e) —C(O)C(HR⁹)OR¹⁰ wherein R⁹ is hydrogen or methyl and R¹⁰ is phenyl optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo; and (f) —S(O)₂R¹¹ wherein R¹¹ is methyl or phenyl, optionally substituted with 1 or 2 substituents selected from C₁₋₄alkyl and halo; or a pharmaceutically-acceptable salt thereof; and (b) determining the effect caused by the compound on the biological system or sample.
 24. The method of claim 23 wherein in the compound of formula (I), R¹ is isopropyl or tert-butyl; and X is selected from: (a) —C(O)OR² wherein R² is methyl or phenyl; (b) —C(O)R³ wherein R³ is phenyl, optionally substituted with 1 or 2 substituents selected from methyl, chloro, fluoro, and —CF₃; furan-2-yl; or thiophen-2-yl; and (c) —C(O)NR⁴R⁵ wherein R⁴ is hydrogen and R⁵ is phenyl optionally substituted with 1 fluoro or chloro. 